[DESCRIPTION!

[invention Title]

POLYMER-METAL HYDRIDE COMPLEXES CONTAINING AROMATIC GROUP AS HYDROGEN STORAGE MATERIALS AND A METHOD OF PREPARING THE SAME

[Technical Field]

The present invention relates to a hydrogen storage material, and a process for preparing the same. More specifically, it relates to a hydrogen storage material which can adsorb or desorb hydrogen under mild condition (for example, for storage at 25 ^° C, 30 atm; for release at 100°C under 2 atm) as compared to conventional storage materials, and dramatically increase the storage amount, and a process for preparing the same. In addition, the invention relates to a polymer-transition metal hydride complex as hydrogen storage materials which provides a large capacity of hydrogen storage in a safe and reversible manner, and a process for preparing the same.

[Background Art] Extensive studies have been performed to employ hydrogen as a clean energy source that does not exhaust carbonic acid gas. However, for practical use as a future energy source, required are three kinds of technical developments: production of hydrogen, storage of hydrogen, and hydrogen fuel cell which converts

hydrogen energy to electric energy. Particularly, in order to convert various vehicles, which use gasoline or light-oil, to those using hydrogen energy, absolutely required is a technique for storing hydrogen which stores a large amount of hydrogen in a safe and convenient manner and enables loading hydrogen on the vehicles .

A number of techniques have been developed as hydrogen storing means, but compression of hydrogen under high pressure (350 atm or 700 atm) , or storing hydrogen in liquid state by chilling it at an extremely low temperature (below -253 ^° C) involves safety problem (such as danger of explosion). As alternative approaches which do not involve safety concern, studies for storing hydrogen by adsorbing it onto another solid material have been continued, and the conventional techniques are as follows:

First one is to utilize metal hydride. By injecting hydrogen into the metal, the metal and hydrogen are chemically bonded to store hydrogen as shown in Fig. l(a). The process has been researched by a number of scholars for decades, and the disclosure by L. Schlapbach and A. Zuttel [Nature 414, 353,

(2001)] with regard to the process lists up the substances including lithium borohydride (LiBH ₄ ) , which had been developed until that time. Due to strong chemical bond between metal and hydrogen atom, however, a high temperature is needed to separate

hydrogen for use, and if the process is repeated, the structure of the metal substance itself is changed to degenerate the hydrogen storage function.

Second one is to utilize metal-organic framework. For example it is to store hydrogen between minute apertures in a substance such as 1,4-benzene dicarboxylate zinc oxide [Zn ₄ O(BDC) ₃ , (BDC=I, 4-benzenedicarboxylate) ] as shown in Fig. 1 (b) . Regarding the process, the achievement of research and development by N. L. Rosi et al. is disclosed in [Science 300, 1127, (2003)]. However, this process gives insufficient maximum hydrogen storage capacity, and involves several disadvantages as in the case of metal hydrides.

As the third, suggested was a process for adsorbing on a surface of material having nano-structure, using carbon nanotubes, carbon nanofibers or graphite nanofibers (GNFs) . For example, as illustrated in Fig. 1 (c) , when Sc atoms are attached on fluorene, it is expected that a large number of hydrogen molecules are to be adsorbed thereon, as was reported by Y. Zhao [Physical Review Letters, 94, 155504, (2005)]. As illustrated in Fig. 1 (d) , when Ti atoms are attached on carbon nanotubes, it is also expected that a large number of hydrogen molecules are to be well adsorbed thereon, as reported by T. Yildirim and S. Ciraci [Physical Review Letters, 94, 175501, (2005)]. Though the maximum capacity of hydrogen storage of these processes is higher than that of

conventional processes, it is still insufficient to be practically utilized in an automobile. The matter of fixing and arranging fluorene or carbon nanotubes has not been contemplated yet, so that consideration of practical use is too early at present. It is reported that 67.5% of hydrogen can be stored in graphite nanofibers [J. Phys . Chem. B, 102, 4253, (1998)]; and that 14~20% of hydrogen can be stored by doping alkali metal on carbon nanotubes [Chen et al., Science 285, 91, (1999)]. However, the reproducibility has been suspected because of matter of containing water and errors in experimental procedure, and the principle of storage is still under dispute.

Fourth one is to utilize polymer metal complex r epr esen ted by [X (CF3SO ₃ ) 2L ₂ ] _n (X is bivalent transition metal and L is an organic ligand) , as is disclosed in Japanese Patent Laid-Open No. 2005-232033. According to the process, a substance such as copper di-4, 4' -bipyridylbistrifluorocarbon sulfate { [Cu (CF3SO3) 2 (bpy) 2] _n } was synthesized, and application examples of the complex to gas separation or a storage device (by using its property to adsorb methane gas) were suggested, but practical utilization cannot be expected because of the adsorption property in high pressure range (several megapascals (MPa)).

Fifth one is disclosed in Japanese Patent Laid-Open No. 2004-275951 which is a process to store hydrogen wherein the surface of noble metal, carbon or porous polymeric substance is

coated to block oxygen to selectively transmit hydrogen, and metal particulates are filled into the porous substance to selectively transmit hydrogen. Transition metal salt such as crystalline nickel sulfate (NiSO ₄ ) was dissolved and it was impregnated in porous zeolite to measure the hydrogen storage capacity. However, it showed 1% by weight level of adsorption in high pressure range of several megapascals (MPa) , so that practical utilization cannot be expected.

Sixth one is disclosed in US Patent Publication No. 20070039473 wherein polymer which can adsorb hydrogen is incorporated in metal oxide to carry out hydrogenation- dehydrogenation. According to the process, aqueous sodium vanadate (NaVC> ₃ ) solution is used to produce vanadium oxide (V ₂ Os) powder via sol-gel displacement. Polymerization is carried out via reaction with aniline, and doping is performed by using a substance such as nickel. But the product shows adsorption under high pressure of 1000 psi or more, so that practical utilization cannot be considered.

Seventh one is to store hydrogen by employing hydrogenation-dehydrogenation using a transition metal catalyst on an expanded π-conjugated substrate, as described in USP 71015330 and Korean Patent Laid-Open No. 2006-0022651. An aromatic compound such as coronene is mixed with a transition metal compound such as titanium dihydride (TiH ₂ ) , and the mixture

is subjected to milling under high temperature (200°C) and high pressure (82bar) to carry out hydrogenation, and then milling under high temperature (150°C) and low pressure (1 bar) to carry out dehydrogenation, so that hydrogen bond is chemically formed and broken. This process requires relatively severe condition of ball milling under temperature of 200 ^° C and under pressure of 82 bar for 2 hours for hydrogenation, and ball milling at 150 ^° C for 7 hours for dehydrogenation. Since it suggests that resonance of methylenic hydrogen occurs as a result of ¹ H NMR, due to hydrogenation of coronene, the reaction time is very long for chemical bonding of hydrogen to π-conjugated system, so that practical utilization is difficult.

[Disclosure] [Technical Problem]

The hydrogen storage material according to the present invention is suggested to overcome the disadvantages and restrictions of conventional hydrogen storage materials as described above. The object of the invention is to prepare polymer-transition metal hydride complex which is a safe and reversible hydrogen storage material with high capacity of hydrogen storage, while suggesting optimal reaction conditions for good yield and stable productivity.

Specifically, another object of the present invention is to

suggest a process for preparing said polymer-transition metal hydride complex and a precursor thereof, the polymer-transition metal halide complex.

Further, another object of the present invention is to provide hydrogen storage material comprising said polymer- transition metal hydride complex, and a hydrogen storage device comprising said hydrogen storage material.

[Technical Solution] The present invention is contrived to solve the above- mentioned problems, and pertains to a polymer-transition metal hydride complex wherein the aromatic ring of a homopolymer or a copolymer of a monomer comprising an aromatic ring has been bonded to transition metal hydride, and a process for preparing the same.

Specifically, the invention relates to a polymer-transition metal hydride complex which is prepared by applying various hydrogen source to a polymer-transition metal compound prepared by chemical reaction of a polymer selected from homopolymers and copolymers of a monomer comprising an aromatic ring with a transition metal compound.

Moreover, the invention relates to a hydrogen storage material comprising said polymer-transition metal hydride complex and a hydrogen storage device comprising said hydrogen storage

material .

Now, the invention is described in more detail. All technical or scientific terms used herein have the same meaning conventionally understood by a person having ordinary skill in the technical field to which the invention belongs, if not specified otherwise.

Repeated descriptions about the same technical constitution or effect as in conventional techniques are omitted for simplicity. The polymer-transition metal hydride complex according to the present invention is a substance wherein a transition metal hydride is bonded to the aromatic ring of homopolymer or copolymer of a monomer comprising aromatic ring. More specifically, it is a polymer-transition metal hydride complex wherein transition metal hydride is bonded to the aromatic ring (Ar) of the homopolymer or copolymer having one or more repeated unit(s) selected from the structures represented by Chemical Formula (1) .

[Chemical Formula 1]

In Chemical Formula (1), Ar is selected from C ₆ -C ₂ O aromatic

rings;

J is selected from -O-, -NH-, -S- and -PH-;

Y is selected from halogen atoms, -NO ₂ , -NO, -NH ₂ , -R ₁ / -OR ₂ ,

-(CO)R ₃ , -SO ₂ NH ₂ , SO ₂ Xi, -SO ₂ Na, - (CH ₂ ) _k SH and -CN, wherein R ₁ through R ₃ are independently selected from Ci~C ₃₀ linear or branched alkyl groups, and C ₆ ~C ₂ o aromatic rings, Xi is a halogen atom, and k is an integer from 0 to 10; and a is an integer from 0 to 4.

The polymer-transition metal hydride complex according to the invention is recognized to have a structure r epr esen ted by Chemical Formula (2).

[Chemical Formula 2]

In Chemical Formula (2), Ar _x and Ar ₂ are independently selected from C ₆ ~C ₂ o aromatic rings;

Ji and J ₂ are independently selected from -0-, -NH-, -S- and -PH-;

Yi and Y ₂ are substituents which are not contained in the polymer chain but having been chemically bonded to the aromatic ring, and independently selected from halogen atoms, -NO ₂ , -NO, -

NH ₂ , -Ri, -OR ₂ , -(CO)R ₃ , -SO ₂ NH ₂ , SO ₂ X ₁ , -SO ₂ Na, - (CH ₂ ) _k SH and -CN, wherein R ₁ through R ₃ in Yi and Y ₂ are independently selected from Ci~C ₃₀ linear or branched alkyl group, and C ₆ ~C ₂ o aromatic rings, Xi is a halogen atom, and k is an integer from 0 to 10; M is one or more transition metal (s) selected from transition metals having the valence of at least 2; p and q represent an integer from 0 to 4; r is an integer from 1 to 2, i represents an integer (valence of M - 1), and m and n are integers satisfying 10 ≤ m+n ≤ 100000 and 0.1 ≤ m/(m+n) ≤ 1.

More specifically, Ar _x and Ar ₂ in Chemical Formula (2) are independently selected from phenylene, naphthylene and anthrylene, and M is recognized to be bonded on the plane of aromatic ring Ari. M is one or more metal(s) selected from transition metals having the valence of at least 2, with being single metal element or different metal elements in one compound. The valence of M preferably ranges from 2 to 7, so that i is an integer from 1 to 6. More preferably, M comprises one or more transition metal (s) such as Ti, V, Sc (which are known to be able to adsorb high volume of hydrogen via Kubas binding) . Thus, i is more preferably from 2 to 4, and most preferably 3.

The present invention provides hydrogen storage material comprising the polymer-transition metal hydride complex r epr esen ted by Chemical Formula (2) or a mixture thereof. With

hydrogen (H ₂ ) being adsorbed, the hydrogen storage material can be r epr esen ted by Chemical Formula (3) : [Chemical Formula 3]

In Chemical Formula (3), M, Ari, Ar ₂ , Ji, J2, Yi, Y2, Pr Qr r, i, m and n are defined as in Chemical Formula (2), and d is an integer from 1 to 10.

Further, the present invention provides a hydrogen storage device which comprises said polymer-transition metal hydride complex or a mixture thereof as a hydrogen storage material .

Now the constitution and effect of an example of polymer- transition metal hydride complex according to the present invention is described in detail by referring to illustrative drawings. The description is intended for a person having ordinary skill in the art to easily carry out the invention, but not intended to restrict the scope of the invention.

As the r epr esen tative polymers to specify polymer- transition metal hydride complex suggested by the present invention, selected were polyaniline (PANI) and poly (2, 6- dimethyl-1, 4-phenylene oxide (dimethyl-PPO) which 1) have

excellent stability under circumstances in laboratories, 2) can be produced in a large scale, and 3) may have relatively large capacity of hydrogen storage with less chemical formula weight of the monomer. As the transition metal bonded on the plane of the aromatic ring in the polymer-transition metal hydride, titanium (Ti) , scandium (Sc) and vanadium (V) , which can adsorb hydrogen via Kubas binding were selected. Among them, titanium (Ti) is most desirable as the transition metal to specify the present invention, since it 1) can adsorb hydrogen molecules more stably, 2) has large amount of deposits, and 3) has no toxicity.

The structure of the polymer-transition metal hydride complex prepared by using the polymer and the transition metal selected according to the invention is now described in more detail.

According to the first embodiment of the invention, the structure of polyaniline-transition metal complex prepared by applying polyaniline (PANI) as the polymer is shown in Fig. 2. Two transition metals form strong chemical bonds on the plane of the aromatic ring for individual monomers of polyaniline polymer, to provide a stable structure.

In the polyaniline-transition metal complex suggested in Fig. 2, maximum three hydrogen molecules can be adsorbed via Kubas bindings between transition metal and hydrogen; the

chemical structure is shown in Fig. 3.

According to the second embodiment of the present invention

(not shown in the figures), in case of poly (2, 6-dimethyl-l, 4- phenylene oxide) -transition metal complex which was prepared by applying poly (2, 6-dimethyl-l, 4-phenylene oxide) as a polymer, two transition metals are chemically bonded on the plane of the aromatic ring of each monomer firmly, to provide a stable structure .

Alike the polyaniline-transition metal complex, maximum three hydrogen molecules can be adsorbed via Kubas bindings with transition metal.

In both structures of polymer-transition metal complex suggested above, calculation methods in first principal quantum mechanics and statistical dynamics were applied in order to observe the adsorption energy between transition metal and hydrogen molecules and the behavior of adsorption/desorption of hydrogen molecules.

As the result of calculation of adsorption energy of transition metal (titanium, scandium, vanadium) and hydrogen molecule, respectively, via precise first principal quantum mechanics, it is elucidated that the complex had a value of electron voltage (eV) from 0.3 to 0.5. This is the most ideal range to store hydrogen around ambient temperature and ambient pressure (1 atm) [Physical Review Letters, 97, 056104 (2006)].

In order to calculate the temperature and pressure range for the behavior of adsorption/desorption of the complex proposed by the present invention and hydrogen molecules, a process of statistical dynamics is applied. The adsorption energy with transition metal per hydrogen molecule is average 0.4 eV in all three metals proposed. Thus it is found that the adsorbed hydrogen can be desorbed with only the temperature increase or pressure decrease to a relatively small extent around ambient temperature and ambient pressure [Physical Review Letters, 97, 056104 (2006) ] .

The standard value (6%) of minimum hydrogen storage amount which was suggested by Department of Energy (DOE) of the United States in order to practically utilize a hydrogen storage material and the hydrogen storage amount of the polymer-titanium hydride prepared from the polymer selected by the present invention were compared hereinbelow. The polymeric formula of the structure wherein Ti is bonded on the plane of the aromatic ring of polyaniline [(C ₆ H ₄ NH^TiH ₁ )] and the structure wherein Ti is bonded on the plane of the aromatic ring of poly (2, 6-dimethyl- 1, 4-phenylene oxide) [ (C ₆ H ₂ (CH ₃ ) ₂ O- 2TiH ₁ ) _n ] with hydrogen stored therein are (C ₆ H ₄ NH- 2TiH ₂ ^• 6H ₂ ) n and (C ₆ H ₂ (CH ₃ ) ₂ O- 2TiH ₁ - 6H ₂ ) n, respectively.

The weight percentage of stored hydrogen (6H ₂ ) with respect to the weight of each polymer [ (C ₆ H ₂ (CH ₃ ) ₂ O- 2TiH ₁ ) _nι

(C ₆ H ₂ (CH ₃ ) ₂ θ'2TiHi) _n ] is about 5.2 to 5.9%, which is very close to the standard value (6%) of minimum hydrogen storage amount suggested by DOE of the United States.

In order to realize the polymer-transition metal hydride complex thus proposed on the basis of the polymer structure model and calculation process as described above, experiments were performed. The detailed experimental and analytical results are described below.

The present invention provides a polymer-transition metal halide complex which is r epr esen ted by Chemical Formula (4), as a precursor for preparing the polymer-transition metal hydride complex.

[Chemical Formula 4]

[In Chemical Formula (4), M, Ar ₃ ., Ar ₂ , Ji, J2, Yi, Y2, P, q, r, i, m and n are defined as in Chemical Formula (2), and X r epr esen ts a halogen atom selected from F, Cl, Br and I.]

The present invention provides a process for preparing a polymer-transition metal halide complex wherein a polymer compound comprising an aromatic ring represented by Chemical

Formula (5) is reacted with alkali metal to activate the aromatic ring, and a metal halide of Chemical Formula (6) is reacted with the activated aromatic ring to obtain a polymer-transition metal halide complex of Chemical Formula (4). [Chemical Formula 4]

[Chemical Formula 5]

[Chemical Formula 6]

MX ₁₊₁

[In the Chemical Formulas (4) to (6), Ar, Ari and Ar2 are independently selected from C ₆ -C ₂ O aromatic rings;

J, Ji and J ₂ are independently selected from -O-, -NH-, -S- and -PH-;

Y, Yi and Y ₂ are independently selected from halogen atoms, -NO ₂ , -NO, -NH ₂ , -R ₁ , -OR ₂ , -(CO)R ₃ , -SO ₂ NH ₂ , SO ₂ Xi, -SO ₂ Na, -

(CH ₂ ) _k SH and -CN, wherein R ₁ through R ₃ in Y, Y ₁ and Y ₂ are independently selected from Ci-C ₃₀ linear or branched alkyl groups, and C ₆ ~C ₂ o aromatic rings, Xi is a halogen atom, and k is an integer from 0 to 10; M is one or more transition metal (s) selected from transition metals having the valence of at least 2;

X is selected from halogen atoms; a, p and q represent an integer from 0 to 4; r is an integer from 1 to 2, i r epr esen ts an integer (valence of M - 1), and m and n are integers satisfying 10 ≤ m+n ≤ 100000 and 0.1 ≤ m/ (m+n) < 1. ]

Here, m means the number of monomers with which the transition metal halide is bonded, and n means the number of monomers which are not bonded with the transition metal halide. Thus, the binding ratio (m/ (m+n) ) of the transition metal halide can be adjusted as desired, and the ratio for a hydrogen storage material preferably is at least 10%.

The polymer compound of Chemical formula (5) is selected from homopolymers or copolymers having one or more repeated unit(s) selected from the structures represented by Chemical Formula (1). Specifically, Ar is selected from phenylene, naphthylene and anthrylene. More specifically, Ar is phenylene. Depending on the number of the repeated unit(s), the molecule may be an oligomer or a polymer with high molecular weight. Specific

compounds include, but are not limited to, poly (2, 6-dimethyl-l, 4- phenylene oxide) [dimethyl-PPO] , poly (1, 4-phenylene oxide) [PPO], polyaniline [PANI], and polymer substances consisting of one or more derivative (s) thereof or copolymer (s) thereof. In the process for preparing the polymer-metal halide complex according to the invention, the reaction can be expressed by two steps as shown in Reaction Formula (1), for instance, if Ar is phenylene and alkali metal is sodium. In Reaction Formula 1, Y, J, X, a, i, m and n are defined as before. [Reaction Formula 1]

In the first step in Reaction Formula (1), a polymer compound (Chemical Formula 5) comprising an aromatic ring is dissolved in solvent, and then subjected to activation to induce ionization of the aromatic ring, by means of alkali metal such as Na, K as a strong base. During the experiment, an excess amount of alkali metal is used to maximize the activity of alkali metal as an electron donor, or the external shape of alkali metal is processed in powder or slices. However, the external shape of alkali metal is not restricted to those shapes.

The temperature of the first step ranges from -100 to 0 ^° C,

preferably from -78 to -20 ^° C. If the reaction temperature is lower than -100 ^° C, the activation rate of Na is insufficient to proceed with sufficient ionization of the polymer compound

(Chemical Formula 5) . If the reaction temperature is higher than 0 ^° C, it is difficult to adjust the activity of alkali metal so that various types of byproducts are produced.

The duration of the reaction under reflux in step (1) is from 1 to 5 hours, preferably from 2 to 4 hours, more preferably from 2 to 3 hours. If the reaction time is less than 1 hour, it is difficult to proceed with sufficient ionization of Compound

(4). If it is more than 5 hours, decomposition of the reactants predominantly occurs. However, the reaction time needs not to be restricted to the above-mentioned range, since the reaction time can be appropriately adjusted depending upon the reaction temperature.

In the second reaction step in Reaction Formula (1), metal halide of Chemical Formula (6) is dissolved in solvent, and the solution of compound of Chemical Formula (5) obtained from the first reaction step is incorporated to solution of compound of Chemical Formula (6) to carry out the reaction to prepare the polymer-transition metal halide complex of Chemical Formula (4). Progress of side-reactions such as cross-linking can be inhibited by controlling the injection rate of the polymer substance of Chemical Formula (5) .

The metal halide of Chemical Formula (6) sensitively reacts upon contacting with air and moisture to be converted to its metal oxide form (stable form), so that all procedures of synthesis and purification are preferably carried out under nitrogen atmosphere, and the organic solvent is preferably used after appropriate purification.

The reaction of the second step in Reaction Formula (1) is carried out within a temperature range from 60 to 120 ^° C, preferably from 80 to 100°C. If the reaction temperature is lower than 60 °C, hydrohalide (HX) gas may be present inside the reactor to inhibit completion of the reaction. If the reaction temperature is higher than 100 ^° C, the aromatic ring of Compound (5) is decomposed.

The reaction is quenched depending upon the production of hydrohalide (HX) gas, but the reaction time is from 3 to 24 hours, preferably from 10 to 20 hours. If the reaction time is less than 3 hours, the reaction may be incompleted. If it is more than 24 hours, decomposition of the product may occur.

After the reaction of the second step, the reaction mixture is purified by using a suitable solvent for removing the unreacted reactants and byproducts, and the organic solvent for purification is then removed by means of a rotary evaporator or distillation under reduced pressure. Drying in vacuo for at least 1 hour, preferably at least 5 hours gives the polymer-

transition metal halide complex.

In the first and second step for preparing the polymer- transition metal halide complex, one or more solvent (s) selected from l-methyl-2-pyrrolidinone, tetrahydrofuran, trichlorobenzene, benzene, toluene, chloroform, chlorobenzene, phenyl ether, pyridine, nitrobenzene, dimethylformamide, dimethyl sulfoxide and benzophenone may be used as the reaction solvent.

The present invention also provides a process for preparing a polymer-transition metal hydride complex r epr esen ted by Reaction Formula (2), wherein the polymer-transition metal hydride complex of Chemical Formula (2) is prepared via substitution of the leaving group (L) of the polymer-transition metal complex of Chemical Formula (7) by hydrogen (H) in the presence of hydrogen source.

[Chemical Formula 7]

[Reaction Formula 2 ]

In Chemical Formula (7) and Reaction Formula (2), M, Ari, Ar ₂ , Ji, J ₂ , Yi, Y2, P, q, r, i, m and n are defined as in Chemical Formula (2), and L r epr esen ts any leaving group which can be substituted by hydrogen (H) , and the type of leaving group is not restricted. Examples of L include halogen atom (X) , -OR4, -NHR ₅ , -SO ₄ and -NO ₃ , and R ₄ and R ₅ are independently selected from Ci ~ Cio linear or branched alkyl groups. The number b is defined by the value (valence of M - I)/ (valence of L). The valence of L means the number of bonding (s) with metal; the valence of L of halogen atom (X) , -OR ₄ , -NHR ₅ or -NO ₃ is 1, while that of SO ₄ ^2" is 2. In case that the valence of M is within the range from 2 to 7, b is an integer from 1 to 6 when the valence of L is 1, while b is a value of 0.5, 1, 1.5, 2, 2.5 or 3 when the valence is 2.

The compound of Chemical Formula (7) can be prepared by chemical reaction of a metal compound selected from metal alkoxides, metal alkylamido compounds, metal nitrates, metal sulfates and metal halides with a polymer comprising an aromatic ring. Preferably, L is a halogen atom (X) . When L is a halogen atom, the polymer-transition metal complex of Chemical Formula

(7) may be expressed by the polymer-transition metal halide complex of Chemical Formula (4).

Now, the process for preparing the polymer-transition metal hydride complex is described by referring to the polymer- transition metal halide complex of Chemical Formula (4) wherein L is a halogen atom, among the polymer-transition metal complexes r epr esen ted by Chemical Formula (7).

As a synthetic process for substituting a halide of a polymer-transition metal halide complex with a hydride, a reaction of hydrodehalogenation using a hydrogen source and a catalyst at the same time, or a radical hydrodehalogenation using a radical reductant and a radical initiator at the same time can be referred as examples. The synthetic process is not restricted to those referred, but any conventional synthetic processes for substituting a halogen atom (X) by hydrogen (H) can be employed.

First, the hydrodehalogenation reaction, which employs a hydrogen source and a catalyst at the same time, uses H2 gas as the hydrogen source, and one or more hydrogen donor (s) selected from the group consisting of phosphites such as sodium hypophosphate (NaH ₂ PO ₂ ) , sodium phosphite (NaH ₂ PO ₃ ) , sodium phosphate (NaH ₂ PO ₄ ) or sodium perphosphate (NaHPOs) ; metal hydrides such as lithium borohydride (LiBH ₄ ) , lithium aluminum hydride (LiAlH ₄ ), sodium borohydride (NaBH ₄ ), sodium aluminum hydride (NaAlH ₄ ), magnesium borohydride (Mg (BH ₄ ) ₂ ), magnesium

aluminum hydride (Mg (AlH ₄ ) 2), calcium borohydride (Ca(BH ₄ J ₂ )A calcium aluminum hydride (Ca (AlH ₄ ) ₂ ) , lithium hydride (LiH), sodium hydride (NaH) , potassium hydride (KH) , magnesium hydride

(MgH ₂ ) and calcium hydride (CaH ₂ ) ; formic acid, organic salts such as hydrazine hydrochloride, and C ₃ ~Ci ₀ 2-hydroxy alkane.

More preferably, the polymer-transition metal hydride complex can be prepared in high yield by carrying out hydrodehalogenation in liquid phase in the presence of a neutralizer selected from one or more hydroxide compounds such as NaOH and KOH, and a noble metal catalyst for 1~12 hours.

In order to overcome the problem of conversion of the polymer-transition metal halide complex as the reactant to a stabilized metal oxide form upon exposure to air or moisture, the amount of hydrogen supply during the reaction is maximized in the reaction mixture by supplying H ₂ gas and the hydrogen donor at the same time. It is more preferable to simultaneously select one or more hydrogen donor (s) from 1) α-hydrogen containing 2- hydroxy alkane having the property that it is relatively easy to be handled at ambient temperature and ready to be released by methyl group (which serves as a leaving group adjacent to α- carbon) , and 2) metal hydrides generating a large amount of hydrogen via hydrolysis under the action of noble metal catalyst under strongly basic condition. As 2-hydroxy alkane, 2-propanol or 2-butanol is more preferably used. As metal hydride, one or

more substance (s) selected from lithium borohydride (LiBH ₄ ), sodium borohydride (NaBH ₄ ) and magnesium borohydride (Mg (BH ₄ ) 2) is (are) more preferably used, with sodium borohydride being most preferable . More specifically, the hydrodehalogenation comprises following steps: a) mixing a polymer-transition metal halide complex; one or more compound(s) selected from lithium borohydride (LiBH ₄ ), sodium borohydride (NaBH ₄ ) and magnesium borohydride (Mg (BH ₄ ) 2) as metal hydride; and 2-propanol or 2-butanol as 2-hydroxy alkane, under nitrogen atmosphere to prepare a reaction mixture; and b) incorporating a noble metal catalyst to the reaction mixture and heating the resultant mixture under reflux with hydrogen gas supply. As the noble metal catalyst, one or more metal (s) selected from Pt, Pd, Ru and Rh can be used. Palladium (Pd) having high activity in hydrodehalogenation, or platinum (Pt) having high activity in hydrolysis of sodium borohydride can be more preferably used. In order to facilitate applications to mass production processes and catalyst recovery, the noble metal catalyst is preferably applied as a heterogeneous catalyst, which is in a solid catalyst form supported on a carrier. The carrier can be selected from carbon substance such as graphite, silica, alumina and titania. The amount of the noble metal catalyst

supported is from 1 to 20% by weight, preferably from 1 to 10% by weight, more preferably from 1 to 5% by weight on the basis of total weight of the carrier and the noble metal catalyst. If the amount is less than 1% by weight, active sites are insufficient to fail to proceed with the reaction. If the amount is more than 20% by weight, problem of high cost occurs due to the use of precious noble metal catalyst.

In step b) , it is preferable to add hydroxide compound in order to inhibit unstable generation of hydrogen from the metal hydride, and as a neutralizer for HX produced during the reaction. The hydroxide compounds include NaOH, KOH, or the like.

For the hydrodehalogenation, the preparation condition was established on the basis of the production parameters such as the individual contents of the polymer-transition metal halide complex as the reactant, the hydrogen donor, the neutralizer, the noble metal catalyst in the reaction mixture, and pressure of H ₂ gas applied, for the purpose of steady production of the polymer- transition metal hydride complex as hydrogen storage material.

The content of the polymer-transition metal halide complex in the reaction mixture is from 0.0001 to IM, preferably from 0.001 to 0.5M, more preferably from 0.01 to 0.1M. If the content in the reaction vessel is less than 0.0001M, production of the product may be insufficient, while if it is more than IM, the byproducts cannot be thoroughly washed during the washing stage of

the product after the reaction.

The content of the metal hydride in the reaction mixture is from 0.0001 to 3OM, preferably from 0.001 to 15M, more preferably from 0.01 to 3M. If the content in the reaction vessel is less than 0.0001M, thorough proceeding of hydrodechlorination may be difficult, while if it is more than 3OM, the by-products cannot be thoroughly washed during the washing stage of the product after the reaction.

The content of 2-hydroxy alkane in the reaction mixture is from 0.0001 to 3OM, preferably from 0.001 to 1OM, more preferably from 0.01 to 3M. If the content in the reaction vessel is less than 0.0001M, thorough proceeding of hydrodechlorination may be difficult, while if it is more than 3OM, the by-products can not be thoroughly washed during the washing stage of the product after the reaction.

The content of the hydroxide compound in the reaction mixture is from 0.0001 to 18M, preferably from 0.001 to 6M, more preferably from 0.01 to 1.8M. If the content in the reaction vessel is less than 0.0001M, neutralization of HCl by-product does not properly occur so that poisoning of the catalyst becomes severe to cause difficulties in completion of hydrohalogenation.

If the content is more than 18M, excessive production of NaCl

(salt formation) may cause the problems in separation thereof.

The content of the noble metal catalyst in the reaction

mixture is from 0.01 to 50 mol%, preferably from 1 to 50 mol% on the basis of the amount of the polymer-transition metal halide complex. If the content of the noble metal catalyst is less than 0.01mol%, thorough proceeding of the reaction may be difficult, while if it is more than 50mol%, better effect can be hardly obtained but provides disadvantages in terms of cost.

The pressure of hydrogen gas supply in step b) is from 1 to 30 bar, preferably from 1 to 20 bar, more preferably from 1 to 10 bar. If the pressure is less than 1 bar, the reaction rate may be lowered, while if it is more than 30 bar, decomposition of the reactant may occur.

The duration of reaction under reflux in step b) is from 1 to 48 hours, preferably from 1 to 24 hours, more preferably from 1 to 12 hours. If the reaction time is less than 1 hour, the reaction may not be completed, while if it is more than 48 hours, decomposition of the reactant may occur.

Second, described below is the radical hydrodehalogenation wherein radical reductant and radical initiator are used at the same time. The radical hydrodehalogenation employs radical reductant as the hydrogen source. One or more radical reductant (s) can be selected from TMS ₃ CH, Bu ₃ SnH, Ph ₃ SnH and Me ₃ SnH. In the radical hydrodehalogenation, radical initiator such as AIBN and VAZO (1, 1-azobis (cyclohexane carbonitrile) ) is employed along with the

radical reductant.

According to the radical hydrodehalogenation, a halide is radicalized and then substituted by hydride by means of reductant to provide polymer-transition metal hydride complex. The radical hydrodehalogenation, likewise said hydrodehalogenation, is carried out under nitrogen atmosphere, and it is preferable to use solvent, if any, that was purified in an appropriate manner, in order to prevent side reaction of producing metal oxide.

Solvent such as tetrahydrofuran, toluene, benzene, dichloromethane and chloroform can be used.

In addition, the present invention provides a process for preparing a polymer-transition metal hydride complex which comprises the steps of

(i) reacting a polymer of Chemical Formula (5) comprising an aromatic ring with an alkali metal to activate the aromatic ring, and reacting it with a metal halide of Chemical Formula (6) to obtain a polymer-transition metal halide complex of Chemical

Formula (4) ; and

(ii) preparing a polymer-transition metal hydride complex of Chemical Formula (2) from the polymer-transition metal halide complex of Chemical Formula (4) in the presence of hydrogen source .

[Chemical Formula 2]

[Chemical Formula 4 ]

[Chemical Formula 5 ]

[Chemical Formula 6 ]

MX _i+1

As a synthetic process for substituting the halide of the polymer-transition metal halide complex by a hydride in step (ii) , a reaction of hydrodehalogenation using a hydrogen source and a catalyst at the same time, or a radical hydrodehalogenation using

a radical reductant and a radical initiator at the same time can be referred as an example. The synthetic process is not restricted to those referred, but any conventional synthetic processes for substituting a halogen atom (X) by hydrogen (H) can be employed.

[Description of Drawings]

Fig. l(a), 1 (b) , l(c) and 1 (d) show chemical structures of three types of hydrogen storage materials according to the conventional techniques.

Fig. 2 shows chemical structure of a novel hydrogen storage material having titanium atom bonded to polyaniline according to one embodiment of the present invention.

Fig. 3 shows the chemical structure wherein hydrogen molecules are bonded as much as possible to the novel hydrogen storage material having titanium atom bonded to an polyaniline according to one embodiment of the present invention.

Fig. 4 schematically shows hydrodehalogenation reaction.

[Mode for Invention]

Now the constitution and effect of one preferable embodiment of the present invention are described in detail by referring to the exemplified drawings. Such description is to enable a person having ordinary skill in the art to which the

invention belongs to carry out the invention with ease, but not intends to restrict the scope of the invention.

[Example 1] Preparation of polyaniline titanium hydride (1) Preparation of polyaniline titanium chloride

To a 250 ml two-necked round-bottomed flask, charged were titanium (IV) chloride (2.9 ml, 0.026 mol) and l-methyl-2- pyrrolidinone (40 ml). Polyaniline (PANI) (4.732 g, 0.052 mol, based on the monomer) thoroughly dissolved in l-methyl-2- pyrrolidinone (30 ml) was reacted with Na at -50°C to be activated, and the mixture was slowly added to the 250 ml two- necked round-bottomed flask. After heating the resultant mixture under reflux at 90 ^° C for 24 hours, the reaction was completed. After cooling to ambient temperature, the reaction mixture was filtered to remove the solvent, washed with hexane (100 ml) and ethyl acetate (100 ml) to remove the residual reactant. Drying in vacuo gave polyaniline titanium chloride in 70% yield. ESI-MS (positive mode), m/z: [C ₆ H ₄ NH ^• 2TiCl ₃ -H] ⁺ multiplet 393-407 (major 397) Anal. CaIc. for C ₆ H ₅ NTi ₂ Cl ₆ : C, 18.00; H, 1.25; N, 3.50. Found: C, 17.85; H, 1.21%; N, 3.46%

(2) Preparation of polyaniline titanium hydride According to the process illustrated in Fig. 4, polyaniline titanium hydride was prepared from polyaniline titanium chloride. A 100 ml three-necked round-bottomed flask was charged with

polyaniline titanium chloride (0.072 g, 0.18 itunol, based on the monomer) thus prepared under nitrogen atmosphere. Sodium borohydride (3 g) and 2-propanol (50 ml) were added thereto, and the resultant mixture was stirred at 65 ^° C for 12 hours. To another flask that had been separately prepared, palladium supported on carbon (Pd/C, Pd content: 5 wt%) (0.1 g) as a catalyst and aqueous sodium hydroxide solution (IM, 20 ml) were added. After stirring for 20 minutes, the solution of polyaniline titanium chloride that had been previously prepared was slowly added, while hydrogen gas was supplied under pressure of 5 bar. The reaction mixture was heated at 65 ^° C under reflux for 12 hours to complete the reaction.

After cooling to ambient temperature, the reaction mixture was filtered to remove the solvent, and distilled water (500 ml) was poured into the mixture. After extracting three times with dichloromethane (200 ml), sodium sulfate (10 g) was added, and the mixture was stirred by using a rotary agitator for 30 minutes, and filtered. Dichloromethane was removed by using a rotary evaporator, and the residue was dried in vacuo to obtain polyaniline titanium hydride in 60% yield. ESI-MS (positive mode), m/z: [C ₆ H ₄ NH ^• 2TiH ₃ -H] ⁺ multiplet 227-235 (major 231) Anal.

CaIc. for C ₆ H ₅ NTi ₂ H ₆ : C, 31.17; H, 4.76; N, 6.06. Found: C, 30.85;

H, 4.67%; N, 5.92%

[Example 2] Preparation of poly (2, 6-dimethyl-l, 4- phenyleneoxide) titanium hydride

(1) Preparation of poly (2, 6-dimethyl-l, 4- phenyleneoxide) titanium chloride A 250 ml two-necked round-bottomed flask was charged with titanium (IV) chloride (2.9 ml, 0.026 mol) and chloroform (40 ml) under nitrogen atmosphere. Then, poly (2, 6-dimethyl-l, 4-phenylene oxide) (dimethyl-PPO) (6.24 g, 0.052 mol, based on the monomer) thoroughly dissolved in chloroform (30 ml) was reacted with Na at -50 °C to be activated, and the mixture was slowly added to the two-necked round-bottomed flask. After heating the resultant mixture under reflux at 90°C for 24 hours, the reaction was completed. After cooling to ambient temperature, the reaction mixture was filtered to remove the solvent, washed with hexane (100 ml) and ethyl acetate (100 ml) to remove the residual reactant. Drying in vacuo gave poly (2, 6-dimethyl-l, 4-phenylene oxide) titanium chloride in 65% yield. ESI-MS (positive mode), m/z: [C ₆ H ₂ (CHs) ₂ ' 2TiCl ₃ -H] ⁺ multiplet 396-420 (major 410) Anal. CaIc. for C ₈ H ₈ OTi ₂ Cl ₆ : C, 23.24; H, 1.94; O, 3.87. Found: C, 22.95; H, 1.87%; O, 3.73%

(2) Preparation of poly (2, 6-dimethyl-l, 4-phenylene oxide) titanium hydride

According to the process illustrated in Fig. 4, poly (2, 6- dimethyl-1, 4-phenylene oxide) titanium hydride was prepared from

poly (2, 6-dimethyl-l, 4-phenylene oxide) titanium chloride.

A 100 ml three-necked round-bottomed flask was charged with poly (2, 6-dimethyl-l, 4-phenylene oxide) titanium chloride (0.074 g,

0.18 mmol, based on the monomer) thus prepared, under nitrogen atmosphere. Lithium aluminum hydride (3 g) and 2-propanol (50 ml) were added thereto, and the resultant mixture was stirred at

65 ^° C for 12 hours. To another flask that had been separately prepared, palladium supported on carbon (Pd/C, Pd content: 5 wt%)

(0.1 g) as a catalyst and aqueous sodium hydroxide solution (IM, 20 ml) were added. After stirring for 20 minutes, the solution of poly (2, 6-dimethyl-l, 4-phenylene oxide) titanium chloride that had been previously prepared was slowly added, while hydrogen gas was supplied under pressure of 5 bar. The reaction mixture was heated at 65 "C under reflux for 12 hours to complete the reaction. After cooling to ambient temperature, the reaction mixture was filtered to remove the solvent, and distilled water (500 ml) was poured into the mixture. After extracting three times with dichloromethane (200 ml), sodium sulfate (10 g) was added, and the mixture was stirred by using a rotary agitator for 30 minutes, and filtered. Dichloromethane was removed by using a rotary evaporator, and the residue was dried in vacuo to obtain poly (2, 6-dimethyl-l, 4-phenylene oxide) titanium hydride in 50% yield. ESI-MS (positive mode), m/z: [C ₆ H ₂ (CHs) ₂ ' 2TiH ₃ -H] ⁺

multiplet 202-210 (major 206) Anal. CaIc. for C ₈ H ₁₄ OTi ₂ : C, 46.60; H, 6.80; O, 7.77. Found: C, 46.36; H, 6.68%; O, 7.54%

[industrial Applicability] The polymer-transition metal hydride complex according to the invention as hydrogen storage material can store and use under a condition approximate to ambient temperature and ambient pressure via Kubas binding between transition metal and hydrogen. In addition, the complex can bind multiple transition metals per molecule since it utilize alkali metal as a strong base to activate the aromatic ring during the course of the preparation and use the activated aromatic ring as a reactive group, so that high weight percentage of stored hydrogen per total material, and weight of hydrogen per unit volume are expected. The process for preparing the polymer-transition metal hydride according to the present invention provides an advantage of preparing the object substance, polymer-transition metal hydride, under stable production condition in a good yield.