SEPARATION OF AROMATIC COMPOUNDS FROM CARBOHYDRATES USING

METAL-ORGANIC FRAMEWORKS

CROSS-REFERENCE TO RELATED APPLICATION(S) This application claims the benefit of US Ser No. 62/382,244, filed: Aug 31, 2017 and

US Ser No. 62/349,986, filed: Jun 14, 2016, which are incorporated herein by reference in their entirety.

STATEMENT REGARDING FEDERALLY-SPONSORED RESEARCH

[0001] This invention was made with government support under Grants DE-FG02- 05ER15696 and DE-SC0012702 awarded by the U.S. Department of Energy. The Government has certain rights to this invention.

BACKGROUND

[0002] In carbohydrate fermentation, aromatic compounds that are produced as byproducts can poison the enzymes which catalyze fermentation. In particular, the breakdown of carbohydrates in lignocellulosic biomass, a source of biomass on earth, may lead to the production of furanic or phenolic compounds, or combinations thereof. Aromatic compounds, including furanic and phenolic compounds, can poison catalysts, enzymes, and fermentation organisms used in the fermentation of carbohydrates (see Leonard, R. H., et al , Ind. Eng. Chem. 1945, 37, 390-395; Clark, T. A, et al. , J. Chem. Technol. Biotechnol. 1984, 34, 101-110; Delgenes, J. P., et al , Enzyme Microb. Technol. 1996, 19, 220-225).

[0003] Furanic compounds, such as 5-hydroxymethylfurfural and furfural, are also green platform chemicals that may be derived from acid-catalyzed dehydration of carbohydrates. One challenge in synthesizing these compounds is to reduce possible decomposition as a result of sequential undesired reaction. These include decomposition to humins, which result from furanics polymerization; or to levulinic and formic acid, via rehydration. To increase furanics yield, various biphasic extraction strategies employing organic solvents have been tried, in tandem with aqueous-phase acid catalysis. However, these strategies often require costly downstream distillation. An alternative is the specific adsorption of the furanic onto a solid surface. However, the selectivity of adsorption has been a limitation, since carbohydrate reactants can also be adsorbed onto the solid surface. [0004] Thus, it is desirable to separate aromatic compounds, such as furanic and phenolic compounds, from carbohydrates, including in fermentation mixtures. There is a need in the art for alternative methods to separate aromatic compounds from carbohydrates, such as sugars.

SUMMARY OF THE INVENTION

[0005] The present disclosure provides methods of separating aromatic compounds from carbohydrates using metal-organic frameworks (MOFs). Thus, in one aspect, provided is a method for separating an aromatic compound from a carbohydrate, wherein the carbohydrate is a monosaccharide or an alpha-linked disaccharide, or a combination thereof, by:

contacting a metal-organic framework with a solution comprising the aromatic compound and the carbohydrate; and

separating the aromatic compound from the carbohydrate in the solution by adsorbing at least a portion of the aromatic compound in the solution onto the metal-organic framework.

[0006] In some variations, the aromatic compound is a furanic compound.

[0007] In some variations, provided is a method that includes:

contacting a carbohydrate with a catalyst or an enzyme to produce a fermentation mixture, wherein the fermentation mixture comprises an aromatic compound and at least a portion of the carbohydrate;

contacting a metal-organic framework with the fermentation mixture; and

separating the aromatic compound from the carbohydrate in the fermentation mixture by adsorbing at least a portion of the furanic compound in the fermentation mixture onto the metal- organic framework.

[0008] In some variations, the aromatic compound is a furanic compound.

BRIEF DESCRIPTION OF THE FIGURES

[0009] The present application can be understood by reference to the following description taken in conjunction with the accompanying figures.

[0010] FIG. 1 depicts an exemplary system for separating carbohydrates from aromatic compounds using a metal-organic framework (MOF).

[0011] FIG. 2A depicts single-component adsorption isotherms of 5-hydroxymethylfurfural, glucose, and fructose on NU-1000 at 297 K. The dashed lines represent the isotherm replicated by the Langmuir parameters (Table 1 in Example 1).

[0012] FIG. 2B depicts single-component adsorption isotherms of furfural and xylose on NU-1000 at 297 K. The dashed lines represent the isotherm replicated by the Langmuir parameters (Table 1 in Example 1). [0013] FIG. 3A depicts a Langmuir plot for 5-hydroxymethylfurfural adsorption on NU- 1000 in a single mode at 297 K.

[0014] FIG. 3B depicts a Langmuir plot for furfural adsorption on NU-1000 in a single mode at 297 K.

[0015] FIG. 4A depicts competitive-mode adsorption isotherms of 5-hydroxymethylfurfural, glucose, and fructose on NU-1000 at 297 K. The dashed lines represent the isotherm replicated by the Langmuir parameters (Table 2 in Example 2).

[0016] FIG. 4B depicts competitive-mode adsorption isotherms of furfural and xylose on NU-1000 at 297 K. The dashed lines represent the isotherm replicated by the Langmuir parameters (Table 2 in Example 2).

[0017] FIG. 5A depicts a Langmuir plot for 5-hydroxymethylfurfural adsorption on NU- 1000 in a competitive mode at 297 K.

[0018] FIG. 5B depicts a Langmuir plot for furfural adsorption on NU-1000 in a competitive mode at 297 K.

[0019] FIG. 6A depicts single-component adsorption isotherms of 5-hydroxymethylfurfural, glucose, and fructose on MSC-30 at 297 K. The dashed lines represent the isotherm replicated by the Langmuir parameters (Table 3 in Example 3).

[0020] FIG. 6B depicts single-component adsorption isotherms of furfural and xylose on MSC-30 at 297 K. The dashed lines represent the isotherm replicated by the Langmuir parameters (Table 3 in Example 3).

[0021] FIG. 7A depicts Langmuir plots for 5-hydroxymethylfurfural (HMF), glucose, and fructose adsorption on MSC-30 in a single mode at 297 K.

[0022] FIG. 7B depicts Langmuir plots for furfural and xylose adsorption on MSC-30 in a single mode at 297 K.

[0023] FIG. 8 depicts a graph of the competitive adsorption of HMF and glucose on NU- 1000, MSC-30, and BP2000 at 297 K.

[0024] FIG. 9 depicts a graph of the competitive adsorption of HMF, glucose, and fructose on NU-1000, MSC-30, and BP2000 at 297 K.

DETAILED DESCRIPTION FO THE INVENTION

[0025] The following description sets forth exemplary methods, parameters and the like. It should be recognized, however, that such description is not intended as a limitation on the scope of the present disclosure but is instead provided as a description of exemplary embodiments.

[0026] In some aspects, provided herein are methods for separating aromatic compounds from carbohydrates, such as sugar, using metal-organic frameworks (MOFs). For example, MOFs can be used to target aromatic compounds without adsorbing sugar during its acid- catalyzed synthesis in aqueous media, and can thus increase aromatic -compound yield as a result of selective sequestration of before degradation. The aromatic compounds may include, for example, furanics or phenolics, or combinations thereof.

[0027] In another example, MOFs can be used for the separation of aromatic compounds from aqueous carbohydrates in solutions for fermentation, where small amounts of aromatic compounds may be present as byproducts, and may poison enzymes that catalyze carbohydrate fermentation. In some variations, the aromatic compounds are furanics or phenolics, or combinations thereof. Thus, in one aspect, provided is a method that includes: contacting a carbohydrate with a catalyst or an enzyme to produce a fermentation mixture, wherein the fermentation mixture comprises an aromatic compound and at least a portion of the

carbohydrate; contacting a metal-organic framework with the fermentation mixture; and separating the aromatic compound from the carbohydrate in the fermentation mixture by adsorbing at least a portion of the aromatic compound in the fermentation mixture onto the metal-organic framework. In some variations, the catalyst is an acid catalyst. In some variations, the aromatic compound is a furanic compound.

[0028] With reference to FIG. 1, exemplary system 100 depicts the methods described herein to separate one or more aromatic compounds from carbohydrates. Column 104

comprises MOF 108. Solution 102 contains a carbohydrate and one or more aromatic compounds, is applied to column 104, and output stream 106 exits the column. In other embodiments, a fermentation mixture containing a carbohydrate and a catalyst is provided to the column containing a metal-organic framework to produce an output stream. In some variations, the output stream 106 comprises a lower concentration of the one or more aromatic compounds than the input stream 102. In other embodiments, the MOF is provided in a solution, and a filtration mechanism is used to produce an output stream. In some embodiments, the aromatic compound is a furanic compound.

[0029] In some embodiments, the MOF is recycled after the adsorption of aromatic compounds. In certain embodiments, the MOF is recycled by rinsing it with water.

[0030] In some embodiments, the carbohydrates in the output stream are used to further produce one or more aromatic compounds or other chemicals. In other embodiments, the carbohydrates in the output stream are in contact with a catalyst or an enzyme after isolation.

[0031] The separation method, including the types of aromatic compounds, carbohydrates, and MOFs used, are further described in detail below.

Metal-Organic Frameworks

Structure of metal-organic frameworks [0032] Metal-organic frameworks (MOFs) are a class of materials formed by coordination bonds between metal-based nodes and organic linkers. The MOFs used in the methods described herein are selected based on various properties, including, for example, pore size, surface area, and choices of metal and linker.

[0033] Certain aspects of the present disclosure relate to methods of separating furanic compounds and carbohydrates using a MOF with an aromatic moiety. In some embodiments, the organic linker of the MOF has an aromatic moiety. In some variations, the aromatic moiety has one aromatic ring. In other variations, the aromatic moiety has two, three, four, five or six aromatic rings that are conjugated together. In certain variations, the aromatic moiety comprises two or more fused rings, for example two, three, four, five or six aromatic rings that are fused. In one variation, the organic linker includes a plurality of aromatic moieties conjugated together. In certain variations, the organic linker has two, three, four, five, or six aromatic rings conjugated with one another. In other variations, the organic linker has between three and six aromatic rings conjugated together. In other variations, the organic linker has four aromatic rings conjugated together, such as pyrene. In certain variations, the organic linker has two, three, four, five, or six fused aromatic rings. In other variations, the organic linker has between three and six fused aromatic rings. In other variations, the organic linker has four fused aromatic rings, such as pyrene.

[0034] In some variations, the organic linker has at least one aromatic heterocyclic ring. In other variations, the organic linker has two, three, four, five, or six aromatic heterocyclic rings that are conjugated with one another. In certain variations, the organic linker has two, three, four, five, or six fused aromatic heterocyclic rings.

[0035] In some variations, the organic linker has an aromatic moiety larger than that of one benzene ring.

[0036] In some embodiments, MOF comprises a plurality of aromatic domains that are connected to the metal. In one variation, the aromatic domain in a MOF refers to the portion of the MOF that has aromaticity. In another variation, the organic linker has an aromatic domain that is less than 5 nm, measured by end-to-end distance of the aromatic domain including a carbonyl group, if applicable. In other variations, the organic linker has an aromatic domain that is less than 2 nm.

[0037] In some variations, the MOF comprises hydrophobic repeating units. In another variation, the MOF comprises hydrophobic repeating units that exhibit π-π interactions with the one or more aromatic compounds to be separated from the carbohydrates. In some variations, the one or more aromatic compounds are one or more furanic compounds, one or more phenolic compounds, or a combination thereof. Without being bound by any theory, MOFs that exhibit π-π interactions with the one or more aromatic compounds may achieve better selectivity for aromatic compounds than MOFs that do not have such interactions, because π-π interactions are absent when MOFs adsorb sugars.

[0038] In some embodiments, the organic linker has a pyrene moiety. In other embodiments, the organic linker has hydrophobic pyrene repeat units.

[0039] In some embodiments, the MOF has a surface area larger than 500 m ² /g. In some variations, the MOF has a surface area smaller than 6000 m ² /g.

[0040] In some embodiments, the MOF comprises a plurality of pores. In one variation, at least a portion of the pores have a diameter greater than 6 A, greater than 7 A, greater than 8 A, greater than 9 A, greater than 10 A, or greater than 15 A. In other variations, the MOF comprises a plurality of pores, wherein at least a portion of the pores have a diameter of less than 10 nm, less than 5 nm, or less than 1 nm. In certain variations, the MOF has pores between 6 A and 10 nm, between 6 A and 1 nm in diameter.

[0041] In some embodiments, the methods for separating carbohydrates and furanic compounds use a MOF with a Zr-based node.

[0042] In some variations, the MOF is hydrothermally stable.

[0043] In some embodiments, the methods for separating carbohydrates and furanic compounds use more than one MOF.

[0044] In some embodiments, the methods for separating carbohydrates and furanic compounds use NU-800, NU-901, NU-1000, NU-1001, NU-1102, or NU-1100, or a

combination thereof.

[0045] The MOF may be provided in alternative formats, such as a multiple adsorption- desorption column format (i.e. as in pressure- swing adsorption) or a MOF-containing membrane. In some embodiments the MOF is incorporated into a membrane, preferably a membrane configured to operate on the principle of permeability - based on a ratio of partitioning and diffusivity; suitable MOF membrane are known in the art, e.g. Qiu et al., Chem. Soc. Rev., 2014, 43, 6116.

Selectivity

[0046] In some aspects, the MOF being used to separate one or more aromatic compounds from a carbohydrate has a higher adsorption capacity of the one or more aromatic compounds than the carbohydrate. In some variations, the MOF has a greater adsorption capacity for adsorbing the aromatic compound than the carbohydrate by 10-fold, 11-fold, 12-fold, 13-fold, 14-fold, or 15-fold; or at least 10-fold, at least 15-fold, at least 20-fold, at least 25-fold, at least 50-fold, or at least 100-fold; or between 10-fold and 100-fold, between 20-fold and 100-fold, between 10-fold and 50-fold, between 10-fold and 20-fold, or between 10-fold and 15-fold. Such a comparison in adsorption capacity is observed in a competitive mode, when both the aromatic compound and the carbohydrate are at the same concentration in solution.

[0047] In some variations, the MOF adsorbs 10-fold, 11-fold, 12-fold, 13-fold, 14-fold, or 15-fold more of the aromatic compound than of the carbohydrate. In certain variations, the MOF adsorbs at least 10-fold, at least 15-fold, at least 20-fold, at least 25-fold, at least 50-fold, or at least 100-fold more of the aromatic compound than of the carbohydrate. In yet other variations, the MOF adsorbs between 10-fold and 100-fold, between 20-fold and 100-fold, between 10-fold and 50-fold, between 10-fold and 20-fold, or between 10-fold and 15-fold more of the aromatic compound than the carbohydrate. In some variations, the aromatic compound is a furanic compound. In some variations, the carbohydrate is glucose, fructose, xylose, or maltose, or any mixtures thereof. In certain variations, the MOF adsorbs one or more aromatic compounds without adsorbing one or more carbohydrates.

[0048] In some variations, the methods for separating carbohydrates and aromatic compounds use a MOF that can produce an output stream comprising the aromatic compound at a concentration of less than 25 mM, less than 24 mM, less than 23 mM, less than 22 mM, less than 21 mM, less than 20 mM, less than 19 mM, less than 18 mM, less than 17 mM, less than 16 mM, less than 15 mM, less than 10 mM, less than 9 mM, less than 8 mM, less than 7 mM, less than 6 mM, less than 5 mM, less than 4 mM, less than 3 mM, less than 2 mM, or less than 1 mM; or between 1 mM and 25 mM, between 5 mM and 25 mM, or between 10 mM and 16 mM. In other variations, the methods for separating carbohydrates and furanic compounds use a MOF that can produce an output stream containing more than 60%, more than 70%, more than 80%, more than 90%, or more than 95% by weight of the carbohydrate. In other variations, the methods for separating carbohydrates and aromatic compounds use a MOF that adsorbs less than 5%, less than 4%, less than 3%, less than 2%, or less than 1% by weight of the carbohydrate in the solution.

[0049] In some variations of the foregoing, the one or more aromatic compounds are one or more of the furanic compounds described herein.

Aromatic Compounds

[0050] Biomass provides an abundant supply of carbohydrates that can be used to produce aromatic compounds via catalyzed dehydration of these carbohydrates. In some variations, the aromatic compounds are furanic compounds, in other variations the aromatic compounds are phenolic compounds. In still other variations, the aromatic compounds comprise a mixture of furanic and phenolic compounds. In certain fermentation reactions, the presence of aromatic compounds such as furanics and/or phenolics can be poisonous for enzymes that catalyze carbohydrate fermentation. Certain aspects of the present disclosure relate to the methods of separating carbohydrates from one or more aromatic compounds that can be produced via carbohydrate fermentation. In some variations, the one or more aromatic compounds is one or more furanic compounds. Certain aspects of the present disclosure relate to the methods of separating carbohydrates from all aromatic compounds that can be produced via carbohydrate fermentation. In some embodiments, the methods disclosed herein can be used to separate the carbohydrates from all furanic compounds that can be produced via dehydration of saccharides

[0051] In some embodiments, the aromatic compound is any compound containing aromaticity. In certain embodiments, the aromatic compound is a furanic compound. In some variations, the aromatic compound is a phenolic compound.

[0052] In some embodiments, the aromatic compound is a furanic compound of formula

(A):

wherein:

R ¹ and R ² are H;

X and Y are independently H, alkyl, OH, C(0)H, C(0)OR ^a , or CH ₂ OH, wherein

R ^a is H or alkyl.

[0053] In some variations, the furanic compound is furfural or 5-hydroxymethylfurfural.

[0054] In other variations, the furanic compound is furan, 2-hydroxymethylfuran, 2,5- dihydroxymethylfuran, 2,5-diformylfuran, 2-furoic acid, or 2,5-furandicaboxylic acid.

[0055] In some embodiments, a mixture of furanic compounds is separated from one or more carbohydrates.

[0056] In some embodiments, furanic compounds such as furfural and 5- hydroxymethylfurfural are separated from glucose, fructose, xylose, or maltose, or a combination thereof. In some embodiments, the furanic compounds are separated from the monosaccharides they are derived from. For example, 5-hydroxymethylfurfural and furfural can be separated from glucose, fructose, and xylose. In other embodiments, the furanic compounds are separated from alpha-linked disaccharides. For example, 5-hydroxymethylfurfural and furfural can be separated from maltose.

Carbohydrates

[0057] Carbohydrates are separated from the one or more aromatic compounds according to the methods described herein. In some variations, the one or more aromatic compounds are one or more furanic compounds. [0058] In some embodiments, a carbohydrate has the formula C _m (H20) _n , where m and n are the same or different integer greater than or equal to 1.

[0059] In some variations, the carbohydrate is a monosaccharide, or an alpha-linked disaccharide, or a combination thereof. In one variation, the carbohydrate is a disaccharide formed by two monosaccharides joined with an alpha-glycosidic bond. In some variations, the carbohydrate is maltose.

[0060] In some variations, the carbohydrate includes simple sugars. For example, in some variations, the carbohydrate is fructose, glucose, or xylose, or any combinations thereof.

[0061] It should be understood that the methods described herein may be used to separate a mixture of carbohydrates from one or more aromatic compounds, including one or more furanic compounds.

Systems

[0062] In some embodiments, the methods for separating carbohydrates and aromatic compounds use a MOF provided in a column. In other embodiments, the MOF is provided in a reactor vessel. In other embodiments, the MOF is provided in the solution containing carbohydrates and aromatic compounds. In other embodiments, the MOF is provided in the fermentation mixture containing carbohydrates and aromatic compounds.

Processing Conditions

[0063] In some embodiments, the solution containing carbohydrates and aromatic compounds are in contact with the MOF for at least 1 minute, at least 5 minutes, at least 10 minutes, at least 15 minutes, at least 20 minutes, at least 30 minutes, or at least 60 minutes; or between 1 and 60 minutes, or between 15 and 45 minutes.

[0064] In some embodiments, the fermentation mixture containing carbohydrates and aromatic compounds are in contact with the MOF for at least 1 minute, at least 5 minutes, at least 10 minutes, at least 15 minutes, at least 20 minutes, at least 30 minutes, or at least 60 minutes; or between 1 and 60 minutes, between 15 and 45 minutes.

[0065] In some embodiments, the solution containing carbohydrates and aromatic compounds are in contact with the MOF at a temperature of at least 250 K, at least 260 K, or at least 270 K; or between 250 K and 310 K, or between 270 K and 280 K.

[0066] In some embodiments, the fermentation mixture comprising carbohydrates and aromatic compounds is in contact with the MOF at a temperature of at least 250 K, at least 260

K, or at least 270 K; or between 250 K and 310 K, or between 270 K and 280 K.

Recycling

[0067] In some embodiments, the methods for separating carbohydrates and aromatic compounds using a MOF comprise recycling of the MOF. In some variations, at least a portion of the aromatic compounds adsorbed on the MOF can be removed by rinsing the MOF with water, and the MOF can be recycled. In some embodiments, the MOF can be used for separating carbohydrates and aromatic compounds after recycling.

[0068] In some embodiments, the methods for separating carbohydrates and aromatic compounds using a MOF produce an output stream comprising carbohydrates, and the output stream can be used for further fermentation reactions. In some variations, the output stream comprising carbohydrates can be used to produce aromatic compounds via dehydration.

EXAMPLES

[0069] The following Examples are merely illustrative and are not meant to limit any aspects of the present disclosure in any way.

Example 1

Adsorption of 5-hydromethylfurfural (HMF), furfural, glucose, fructose, and xylose on

NU-1000 in a single mode

[0070] This example demonstrates the affinity of certain furanic compounds and certain carbohydrates with NU-1000 through single-component adsorption experiments in aqueous solution. The furanic compounds were 5-hydroxymethylfurfural (HMF) and furfural. The carbohydrates were glucose, fructose, and xylose. The furanic compounds and carbohydrates were all obtained from commercially available sources.

[0071] An aqueous stock solution containing a single component (for single-component adsorption) with high concentrations was prepared in a volumetric flask. The stock solution was used as-is or after dilution in water (18 ΜΩ cm). NU-1000 of 5 mg was dispersed in 1.5 mL of the aqueous solution. The suspension was ultrasonicated for 1 min to disperse the NU-1000, vortexed for at least 30 min at 297 K, and then filtered with a syringeless filter device equipped with a polytetrafluoroethylene membrane (0.2 μιη mesh). The amount of residual compound in the liquid-phase filtrate was quantified by high-performance liquid chromatography (HPLC) equipped with a carbohydrate analysis column (07.8 x 300 mm, mobile phase 5 mM H ₂ SO ₄ 0.6 mL min ^"1 , column temperature 323 K), with an absolute calibration method. The subtraction of mass of furanic/carbohydrate detected by HPLC from that of compound charged gave an uptake.

[0072] All isotherms for the furanic compounds tested exhibited Type I adsorption behavior, where uptakes increase steeply in the lower concentration range and plateau at higher concentrations. The adsorption was analyzed using the Langmuir equation. This is in contrast to glucose, fructose, or xylose on NU-1000. See FIGS. 2A and 2B. The Langmuir equation [Eq. (SI)] gives the adsorption equilibrium constant (K _ads ) and adsorption capacity (Q _max ) for each isotherm. ads ¾^max 1 \ where C is the equilibrium concentration and Q is the uptake. This equation is transformed into Eq. (S2), which represents the Langmuir plot.

- =— + (S2)

Q Q max. ads *^max

[0073] The estimated Langmuir parameters for furanic compounds and carbohydrate adsorption on NU-1000 at 297 K in a single mode are summarized in Table 1.

Table 1. Langmuir parameters for furanic and carbohydrate adsorption on NU- 1000 at

297 K in a single mode.

. , , Langmuir parameter

Adsorbate _{LaJ Λ} — _LbJ n

^ads M kfmax mg gNU-1000

HMF 120 240

Glucose 0 0

Fructose 0 0

Furfural 28 467

Xylose 0 0

[a] Adsorption equilibrium constant, [b] Adsorption capacity.

[0074] These isotherms observed for the furanic compounds have high enthalpies of adsorption. Table 1 above summarizes the adsorption equilibrium constant ( _a ds) and adsorption capacity (2 _max ), which are obtained from a fit of the Langmuir plots. See FIGS. 3A and 3B. The K _ai is values for HMF and furfural are calculated to be 120 M ^"1 and 28 M ^"1 , respectively, in Table 1. The adsorption capacity of NU- 1000 MOF is high on a mass-fraction basis (2 _max values of 240 mg g u-iooo - ¹ for HMF and 467 m§ gNu-iooo for furfural, Table 1), and comparable to other adsorbents of furan compounds consisting of carbon (See Table 3).

[0075] In contrast to HMF and furfural, NU- 1000 showed no affinity for glucose, fructose or xylose in FIGS. 2A and 2B and Table 1 in single-component adsorption mode. These results indicate the lack of affinity of NU- 1000 for simple monomeric sugars (including glucose, xylose and fructose), while exhibiting higher affinity toward furanic compounds (HMF and furfural).

[0076] Based the data in this Example, NU-1000 (an exemplary MOF) was observed to selectively adsorb furanic compounds rather than the monosaccharides tested.

Example 2

Adsorption of 5-hydromethylfurfural (HMF), furfural, glucose, fructose, and xylose on

NU-1000 in a competitive mode

[0077] This example demonstrates the application of NU- 1000 to separate furanic compounds from a multicomponent sugar-furanics aqueous mixture. Such separation may be applied, for example, in the purification of sugar solutions for fermentation, or in sequestration of the furanics product from the reaction mixture to increase the yield of furanics synthesis from sugars, avoiding sequential reactions. A method similar to that detailed in Example 1 was used to demonstrate adsorption of HMF, furfural, glucose, fructose, and xylose on NU-1000 in a competitive mode at 297 K, where both the furanic compound and the carbohydrate are present at the same time in the aqueous solution mixture. FIGS. 4A and 4B show competitive-mode adsorption isotherms of different furanics and sugars on NU-1000. For C6 compounds, NU- 1000 adsorbs only HMF from the aqueous solution mixture, with 100% retention of glucose and fructose in the solution, even at a high concentration of 0.2 M (FIG. 4A). Similarly, NU-1000 adsorbs furfural, with a lack of xylose uptake (FIG. 4B). These results demonstrate the lack of affinity of NU-1000 for simple monomeric sugars. This leads to an infinite calculated adsorption ratio of furanics to carbohydrates in a competitive mode, when using NU-1000 for both C6 and C5 compounds.

[0078] The Langmuir plots are presented in FIGS. 5A and 5B. The estimated Langmuir parameters for furanics and carbohydrate adsorption on NU-1000 at 297 K in a competitive mode are summarized in Table 2.

Table 2. Langmuir parameters for furanic and carbohydrate adsorption on NU-1000 at

297 K in a competitive mode.

. , , Langmuir parameter

Adsorbate ^ads ¾ / zivr ¹ n kf—max M /mg a ¹¹

gNU-1000

HMF 96 292

Glucose 0 0

Fructose 0 0

Furfural 26 457

Xylose 0 0

[a] Adsorption equilibrium constant, [b] Adsorption capacity

[0079] The Example demonstrates that NU-1000 (an exemplary MOF) was observed to selectively adsorb furanic compounds from aqueous solution mixtures containing sugars.

Example 3

Adsorption of 5-hydromethylfurfural (HMF), furfural, glucose, fructose, and xylose on

MSC-30 in a single mode

[0080] For comparison, commercial mesoporous carbon material MSC-30 was tested using the same method as described in Example 1. All isotherms observed in this study exhibited Type I behavior (i.e., Langmuir isotherm), except for glucose, fructose, or xylose on MSC-30 (FIGS. 6A and 6B). The Langmuir equation [Eq. (SI)] gives the adsorption equilibrium constant (K _adS ) and adsorption capacity (Qm _a x) for each isotherm, which is transformed into Eq. (S2), representing the Langmuir plot (FIGS. 7A and 7B). The estimated Langmuir parameters for furanics and carbohydrate adsorption on MSC-30 at 297 K in a single mode are summarized in Table 3. Table 3. Langmuir parameters for furanic and carbohydrate adsorption on MSC-30 a single mode at 297 K.

Langmuir parameter

Adsorbate

HMF 714 716

Glucose 82 208

Fructose 43 170

Furfural 194 699

Xylose 47 134

[a] Adsorption equilibrium constant, [b] Adsorption capacity.

[0081] This Example demonstrates that MSC-30, a carbon material, exhibits high affinity for furanics, but it also adsorbs simple sugars. In contrast, NU-1000, as an exemplary MOF, exhibits high affinity for furanic compounds, but does not exhibit detectable adsorption capability for simple sugars, as shown in the data of Examples 1 and 2 above.

Example 4

Adsorption of HMF and Glucose on MOF NU-1000, MSC-30 and BP2000

[0082] This Example demonstrates the selective removal of HMF as a representative aromatic compound in fermentation mixtures, using MOF NU-1000.

[0083] This example was performed using a method similar to the procedure described in Example 2 above. An aqueous solution comprising 8 mM HMF and 1 ImM glucose was ised. 1.5 mL this solution was then treated with 25 mg of MOF NU-1000, amorphous carbon MSC- 30, or amorphous carbon BP2000 at 297 K. FIG. 8 is a graph depicting the amount of HMF and glucose removed from the solution by the NU-1000, MSC-30, or BP2000.

[0084] As shown in FIG. 8, NU-1000 removed 80% of the HMF originally present in the solution, while no glucose adsorption occurred on NU-1000. In contrast, amorphous carbon MSC-30 adsorbed 99% of HMF from solution (a higher amount relative to NU-1000), but also adsorbed more than 2.3-fold more glucose than HMF. This resulted in MSC-30 removing 18% of the sugar present in the 111 mM glucose solution mixture. Amorphous carbon BP2000 removed less HMF than MSC-30, and, like MSC-30, BP2000 also resulted in removal of sugar. BP2000 removed 12% of sugar originally present in the 111 mM glucose solution mixture. These data demonstrate the selective removal of aromatic compound HMF from an aqueous mixture of HMF and glucose with NU-1000, without the adsorption of sugar from the same aqueous solution mixture. Such selective removal was not observed with amorphous carbons MSC-30 and BP2000, since these also resulted in adsorption of sugar.

[0085] Without being bound by any theory, selective HMF removal (i.e. without also removing sugars from the feed solution) may involve π-π interactions with the NU-1000; such interactions are absent when adsorbing sugars. Thus, good selectivity of HMF adsorption in the presence of sugars may indicate good selectivity with the other aromatic compounds present in lignocellulose-derived aqueous sugar-feed solutions.

Example 5

Adsorption of HMF, Glucose, and Fructose on MOF NU-1000, MSC-30 and BP2000

[0086] This Example demonstrates the selective removal of HMF in a mixture comprising two sugars, glucose and fructose.

[0087] This example was performed following the general procedure described in Example 3 above. An aqueous solution comprising 40 mM each of HMF, fructose, and glucose was used. 1.5 mL of this aqueous solution was treated with 50 mg of MOF NU-1000, amorphous carbon MSC-30, or amorphous carbon BP2000 at 297 K. FIG. 9 is a graph depicting the amount of HMF, glucose, and fructose removed from the solution by the NU-1000, MSC-30, or BP2000.

[0088] MOF NU- 1000 removed 74% of the HMF originally present in solution

(corresponding to an adsorbed HMF amount of 112 mg gadsorbent ^{- 1} )- No glucose adsorption occurred with NU-1000. In contrast, while amorphous carbon MSC-30 removed 98% of the HMF originally present in solution (corresponding to an adsorbed HMF amount of 148 mg gadsorbent ^{" 1} )) it also adsorbed 30% of the glucose and 21% of the fructose present in the original aqueous solution mixture. Using amorphous carbon BP2000, less HMF as removed compared to MSC-30 (corresponding to 96% of the HMF originally present in the aqueous solution mixture), but BP2000 also resulted in removal of 16% of the glucose and fructose that was originally present in the aqueous solution mixture.

[0089] Again, these data demonstrate the selective removal of aromatic compound HMF from an aqueous mixture of HMF, glucose, and fructose with NU-1000, without the adsorption of sugar from the same aqueous solution mixture. Such selective removal was not observed with amorphous carbons MSC-30 and BP2000, since these also resulted in adsorption of sugar.