APPLICATIONS THEREOF"

TECHNICAL FIELD

The present disclosure relates to a polymer comprising repeating tetra phenyl pyrene monomer unit(s). The disclosure further relates to method of arriving at said polymer and methods of detecting, removing and recovering compounds by employing said polymer. Further, use of the polymer for the detection, removal and recovery of various compounds such as volatile organic compound, polycyclic aromatic hydrocarbon and aromatic pollutant is also disclosed.

BACKGROUND AND PRIOR ART OF THE DISCLOSURE

Detection, removal and recovery of toxic components such as volatile organic compounds (VOCs), polycyclic aromatic hydrocarbons (PAHs), and aromatic pollutants is very important since they cause damage to human health and environment. Presently available solutions are based on porous silica, POMs, graphene/carbon nanotubes and functionalized polymers which can perform only one function, i.e. either detection or removal without recovery. Moreover, large-scale production of these materials is inefficient due to the high costs involved. Further, sensors based on turn-off fluorescence are not efficient in quick detection due to background emission.

Luminescent porous materials, which combine the advantages of porosity and guest- responsive (typically gases and solvent molecules) signalling, are the solid-state analogues of well studied photo-functional molecular cages in solution. Recently, many crystalline framework materials like co-ordination polymer/metal organic, covalent organic and periodic mesoporous silica have been constructed with chromophoric ligands, which showed guest-induced photo-electronic properties like energy transfer and photoconductivity. On the other hand, polymeric and self- assembled systems that can swell or gel in presence of solvent guest molecules have been used as superabsorbents. Though the superabsorbent materials for water uptake have already been commercialized, the design of corresponding analogues for organic solvent uptake, which are of great importance for removing organic pollutants and, remains a challenge. Further, although the microporous polymers have been extensively studied for gas adsorption, the properties characteristic of π-conjugated segments or dynamic networks, such as signal response and solvent uptake, is not known.

Hence, there is a need for a material which can selectively detect, remove and help in recovery of toxic components, and which have properties such as large scale synthesis, low cost, reusable, and stable at different environmental conditions and in different mediums.

The present disclosure addresses the abovementioned drawbacks of the prior art.

BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES

In order that the disclosure may be readily understood and put into practical effect, reference will now be made to exemplary embodiments as illustrated with reference to the accompanying figures. The figures together with a detailed description below, are incorporated in and form part of the specification, and serve to further illustrate the embodiments and explain various principles and advantages, in accordance with the present disclosure where: Figure 1 depicts the porous and luminescent functionality of Py-PP. a) Extended molecular structure of Py-PP, based on the energy minimized geometry of the basic structural unit, b) N2 gas sorption isotherms (77 K) of desolvated polymer (filled circles shows adsorption and empty circles shows desorption). c) Fluorescence spectrum of the desolvated polymer powder measured with a front-face geometry (P0 is the saturated vapor pressure of the gas at 77 K, exc = 380 nm); d) energy minimized geometry of tetra phenyl pyrene; e) scheme for the detection, removal and recovery of VOCs; f) photograph showing the fluorescence response of of Py-PP in the presence and absence of VOCs. ( exc = 365 nm, VOC concentration is 10 ppm). Figure 2 depicts the synthesis of Py-PP polymer of the present disclosure.

Figure 3 depicts the solid-state ¹³ C-CP-TOSS NMR spectrum of Py-PP polymer. Figure 4 depicts the solid-state FT-IR spectra of BDA, TBP and Py-PP polymer.

Figure 5 depicts the PXRD pattern of Py-PP polymer.

Figure 6 depicts the EDX analysis and SEM image of Py-PP polymer. Figure 7 depicts the excitation and emission spectra of Py-PP polymer ( exc = 380 nm, Emission = 540 nm).

Figure 8 depicts the TGA (thermogravimetric analysis) profile of Py-PP polymer measured under N ₂ atmosphere.

Figure 9 depicts the dynamic nature of Py-PP framework, a) Solvent sorption isotherms of Py-PP for toluene (293 K) and for water (298 K), (sample is degassed at 483 K before measurement and equilibrium time is 500 sec); b) Fluorescence enhancement and c) picosecond life time decay profiles of Py-PP (monitored at respective max) after treating with different organic solvents; d) Time dependent fluorescence response of Py-PP after treating with toluene (inset shows the photograph of fluorescence change in Py-PP in 60 min after treating with toluene, exc = 365 nm). (P ₀ is the saturated vapor pressure of the respective adsorbates, fluorescence measurements are done with a front-face geometry, exc = 380 nm) Figure 10 depicts the swelling properties of Py-PP. Swelling behaviour of Py-PP, expressed in terms of Q% and H% respectively, in various organic solvents that possess different polarity.

Figure 11 depicts the SEM image of Py-PP gel in ODCB.

Figure 12 depicts the photograph of swelled sample of Py-PP (20 wt%) in toluene indicating no release of solvent after swelling under STP

Figure 13 depicts the photograph of swelled sample of Py-PP (20 wt%) in CHCI ₃ a) under normal day light and b) under UV-light, which shows visible volume increase and enhanced blue shifted emission up on swelling in CHCI ₃ and there is no release of solvent under STP.

Figure 14 depicts the bucky-ball soaking of Py-PP. a) Photographs of a saturated solution of C ₆ o in toluene (2 mg mL ^"1 ) before and after treatment with Py-PP and schematic representation of C ₆ o-loaded Py-PP. b) N ₂ adsorption isotherms (77 K). c) Solid-state emission spectra and d) picosecond lifetime decay profiles (monitored at λ= 540 nm) of Py-PP with (red) and without C ₆ o (black). P ₀ is the saturated vapour pressure of the gas at 77 K, fluorescence measurements are done with a front-face geometry, ^ ==380 nm.

Figure 15 depicts the nanosecond transient absorption spectrum of Py-PP-C ₆ o adducts dispersion in chloroform. The 490 nm peak is assigned to the pyrene radical cation and the broad absorption in the 500-700 nm is due to the Si-S _n transitions of pyrene. Figure 16 depicts the photograph of toluene gel of Py-PP (5 wt% w.r.t toluene) containing 15 wt% (w.r.t Py-PP) of C ₆ o.

STATEMENT OF DISCLOSURE

Accordingly, the present disclosure relates to a polymer (Py-PP) comprising plurality of tetra phenyl pyrene monomer unit, wherein said polymer is represented by formula I:

Formula I

wherein, n is greater than 1; a method of obtaining a polymer (Py-PP) comprising plurality of tetra phenyl pyrene monomer unit, as claimed above, said method comprising acts of: (a) reacting 1,3,6,8-tetrabromopyrene and benzene 1 ,4-diboronic acid to obtain a first mixture, (b) treating the first mixture with alkyl amide, followed by adding potassium carbonate and palladium(O) complex to obtain a second mixture, and (c) stirring the second mixture to obtain the said polymer; a method of obtaining a compound from a sample, said method comprising acts of: (a) contacting polymer (Py-PP) as claimed above, with the sample for absorbing of the compound within the sample, and (b) optionally, recovering the absorbed compound from the polymer to obtain the said compound.

DETAILED DESCRIPTION OF THE DISCLOSURE

The present disclosure relates to a polymer (Py-PP) comprising plurality of tetra phenyl pyrene monomer unit(s), said polymer represented by formula I:

Formula I

wherein, n is greater than 1.

In an embodiment of the present invention, a structure of the polymer is represented by formula II:

Formula II

In another embodiment of the present invention, the polymer comprises pyrene chromophore and exhibits fluorescence.

In yet another embodiment of the present invention, the polymer is amorphous, hydrophobic and microporous, having pore size up to about 2 nm.

In still another embodiment of the present invention, wherein the polymer is stable up to temperature ranging from about 500 °C to about 550 °C.

The present disclosure further relates to a method of obtaining a polymer (Py-PP) comprising plurality of tetra phenyl pyrene monomer unit, as claimed above, said method comprising acts of: (a) reacting 1,3,6,8-tetrabromopyrene and benzene 1,4- diboronic acid to obtain a first mixture, (b) treating the first mixture with alkyl amide, followed by adding potassium carbonate and palladium(O) complex to obtain a second mixture, and (c) stirring the second mixture to obtain the said polymer.

In an embodiment of the present invention, the step further comprises purifying the polymer by cooling the obtained polymer to room temperature, followed by filtering and washing with organic solvent to obtain a precipitate.

In another embodiment of the present invention, the precipitate is dried and extracted with organic solvent to obtain purified polymer.

In yet another embodiment of the present invention, the 1,3,6,8-tetrabromopyrene and the benzene 1 ,4-diboronic acid are present in molar ratio ranging from about 0.5:2 to about 2:0.5 and reacted in presence of N ₂ .

In still another embodiment of the present invention, the concentration of 1,3,6,8- tetrabromopyrene ranges from about 0.1 millimoles per litre to about 1.0 millimoles per litre and the concentration of benzene 1 ,4-diboronic acid ranges from about 0.2 millimoles per litre to about 2.0 millimoles per litre.

In still another embodiment of the present invention, the alkyl amide is selected from a group comprising dimethylformamide or dimethyl acetamide or a combination thereof.

In still another embodiment of the present invention, after the treatment with alkyl amide, the mixture is subjected to degassing.

In still another embodiment of the present invention, the palladium(O) complex is tetrakis(triphenylphosphine)-palladium(0) and wherein, the step further comprises degassing and purging the second mixture.

In still another embodiment of the present invention, the stirring is carried out at temperature ranging from about 100 °C to about 160 °C and for time period ranging from about 12 hours to about 48 hours.

In still another embodiment of the present invention, the drying is carried out at a temperature ranging from about 50°C to about 60°C and the extraction is carried out for time period ranging from about 3 hours to about 15 hours.

In still another embodiment of the present invention, the organic solvent is selected from a group comprising methanol, dichloromethane, toluene and tetrahydrofuran, or any combination thereof.

The present disclosure further relates to a method of obtaining a compound from a sample, said method comprising acts of: (a) contacting polymer (Py-PP) as claimed above, with the sample for absorbing of the compound within the sample, and (b) optionally, recovering the absorbed compound from the polymer to obtain the said compound.

In an embodiment of the present invention, the above step optionally comprise stirring or sonication or a combination thereof.

In another embodiment of the present invention, the absorption of the compound from the sample by the polymer ranges from about 8 times to about 20 times with respect to the weight of the polymer and wherein the absorption takes place within time period ranging from about 5 seconds to about 1 minute.

In yet another embodiment of the present invention, the concentration of the compound within the polymer ranges from about 90% to about 99%.

In still another embodiment of the present invention, the recovering is carried out by method selected from group comprising squeezing, distillation, washing and evaporation or any combination thereof; and the recovery of the absorbed compound from the polymer ranges from about 90% to about 100%.

In still another embodiment of the present invention, upon obtaining the compound, the recovery of the polymer is 100% and the polymer is reusable for number of cycles ranging from about 20 to about 30.

In still another embodiment of the present invention, the absorption is carried out via non-covalent interactions selected from a group comprising van der Waal's interaction, π-π interaction and host-guest interaction or any combination thereof.

In an embodiment of the present invention, the compound is selected from a group comprising volatile organic compound, polycyclic aromatic hydrocarbon and aromatic pollutant or any combination thereof.

In another embodiment of the present invention, the sample is an aqueous medium comprising the compound.

In yet another embodiment of the present invention, minimum concentration of the compound is about 5 parts per million.

As used herein, the term 'compound' used in the present disclosure encompasses a group of compounds selected from but not limited to volatile organic compounds (VOCs), polycyclic aromatic hydrocarbons (PAHs) and aromatic pollutants.

As described above, the present disclosure provides for a hydrophobic superabsorbent polymer (Py-PP) which can selectively detect by turn-on fluorescence mechanism, remove and recover various VOCs (volatile organic compounds). Because of its porous structure, the VOCs percolates deep inside the Py-PP through van der Waal's, π-π and host-guest interactions and enhances the emission of it which is detected as signal. In an embodiment, this Py-PP is more selective to aromatic solvents such as benzene, toluene and ODCB (orthodichlorobenzene). The sensitivity of the VOC detection is remarkable and is in the range of around 5-10 ppm. In an embodiment, the sensitivity is detected in a closed chamber wherein, VOC having different concentrations (1 to 100 ppm) are kept and Py-PP is introduced into that chamber. The enhancement is observed in the fluorescence under 365 nm UV-lamp. The sensitivity of the VOC detection is found to be in the range of 5-10 ppm. Further, it is observed that the enhancement is evident with the naked eye if the VOC concentration is 10 ppm or above.

The present disclosure further discloses the guest responsive reversible swelling and fluorescence signalling properties of a dynamic, microporous polymer network (Py- PP) which is rendered photo-functional with pyrene chromophores. The hydrophobic nature of the porous network further allows the phase-selective swelling by the instantaneous absorption of a broad range of organic solvents at room temperature. Thus, the organic microporous polymer with a dynamic guest-induced 'swelling' backbone showcases remarkable superabsorbent properties. Further, the organic microporous polymers with conjugated backbones as revealed in this disclosure possesses both luminescent and dynamic functionality and employs the 'turn-on' fluorescence mechanism to get quick amplification during the detection process. In an embodiment of the instant disclosure, the Py-PP is synthesized using Suzuki coupling reaction between two readily available commercial reactants 1,3,6,8- tetrabromopyrene (TBP) and benzene 1 ,4-diboronic acid (BDBA), which are employed in the molar ratio ranging from about 0.5:2 to about 2:0.5. In a preferred embodiment, the molar ratio of 1,3,6,8-tetrabromopyrene (TBP) and benzene 1,4- diboronic acid (BDBA) is 1 :2.

In another embodiment of the present disclosure, various techniques are employed for characterization procedures. The following provides for the major techniques followed for various characterization processes employed in the present disclosure- Scanning Electron Microscopy (SEM): SEM measurements are performed on a Lica- S440I by keeping the samples on copper substrate followed by heating at 150 °C under vacuum and measurements are done with an accelerating voltage of 10 kV. Optical Measurements: Electronic emission spectra are recorded on Perkin Elmer Ls55 Luminescence Spectrometer. Fluorescence spectra of solid powders are recorded in front-face

geometry with 380 nm wavelength.

Laser Flash Photolysis: Flash photolysis is carried out using a Nd:YAG laser source producing nanosecond pulses (8 ns) of 355 nm light with the energy of the laser pulse being around 200 mJ. Dichroic mirrors are used to separate the third harmonic from the second harmonic and the fundamental output of the Nd-YAG laser. The monitoring source is 150W pulsed xenon lamp, which is focused on the sample at 90_ to the incident laser beam. The beam emerging through the sample is focused onto a Czerny-Turner monochromator using a pair of lenses. Detection is carried out using a Hamamatsu R-928 photomultiplier tube. Transient signals are captured with an Agilent infinium digital storage oscilloscope and the data is transferred to the computer for further analysis.

NMR Measurements: Solid state ¹³ C NMR CPTOSS measurements are performed on

BruckerAvance 400 (400 MHz) spectrometer with MAS rate of 5 kHz.

FT-IR Measurements: Infrared (IR) spectra are recorded on small amount of the samples embedded in KBr pellets using a BrukerFT-IR spectrometer.

Thermo Gravimetric Analysis (TGA): Thermogravimetric analysis (TGA) is carried out (Metier Toledo) in nitrogen atmosphere (flow rate 50 mLmin ^"1 ) in the temperature range 30-700 °C (heating rate 5 °C/min).

Elemental Analysis: CHNS analyses are carried out using Thermo Scientific Flash

2000 Elemental Analyzer.

Powder X-ray Diffraction: Powder XRD pattern of the compounds are recorded by in Bruker

D8 Discover (40 kV, 30 Ma) instrument using Cu Ka radiation (2Θ = 0.8-60°).

Computational details: The tetraphenyl pyrene monomer is optimized using Gaussian- 09 suite of programs. The optimization is carried out within Denisty Functional Theory (DFT) using B3LYP hybrid exchange-correlation functional and 6-31G basis set. The optimised geometries are visualised using Visual Molecular Dynamics (VMD). In another embodiment of the instant disclosure, the experiments conducted using Py- PP showcases that it takes almost 10-20 times of various VOCs than its own weight and releases 50-60 % of it by simple hand squeezing. After drying, the Py-PP material is ready to use and shows similar uptake for many cycles and it is stable up to 500°C. It also differentiates different VOCs based on their polarity.

In an exemplary embodiment of the present disclosure, the Py-PP is employed to sensitively detect, remove and recover VOCs, PAHs (polycyclic aromatic hydrocarbons) and aromatic pollutants.

Additional embodiments and features of the present invention will be apparent to one of ordinary skill in art based upon description provided herein and the examples provided below. However, the examples and the accompanying figures should not be construed to limit the scope of the present invention.

Example 1

Synthesis of Py-PP polymer

The synthesis of Py-PP polymer of the present disclosure is illustrated in figure 2. The synthesis procedure is as follows-

Step 1

Py-PP is synthesized by mixing 1,3,6,8-tetrabromopyrene (TBP) and benzene 1,4- diboronic acid (BDBA) in the molar ratio ranging from about 0.5:2 to about 2:0.5 in the N ₂ atmosphere. In a preferred embodiment, the molar ratio of 1,3,6,8- tetrabromopyrene (TBP) and benzene 1 ,4-diboronic acid (BDBA) is 1 :2.0. In another embodiment, molar concentrations of each of TBP and BDBA components range from about 0.1-1.0 mmol and 0.2-2.0 mmol respectively. This mixture is treated with dimethylformamide [DMF] or Dimethyl acetamide [DMAc] (10ml-20 ml) of DMF or DMAc for 0.2 mmol of TBP) and the resulting mixture is degassed by 1-3 freeze- pump-thaw cycles, to remove unwanted/excess dissolved gases such as Oxygen. Step 2

To the mixture obtained in step 1, 2M K ₂ CO ₃ in water (about 1 mL-4 mL solution) and tetrakis(triphenylphosphine)-palladium(0) [45 mg, 38.9 μιηοΐ] are added followed by degassing by 1-3 freeze-pump-thaw cycles.

Step 3

The resultant mixture obtained from step 2 is purged with an inert gas such as N ₂ for 1-5 times and continuously stirred at 100°C-160 °C in a schlenk flask for a duration of 12 hours-48 hours. This is done to ensure the desired functionality and properties of the polymer.

The above three steps are widely known in the chemical industry as Suzuki coupling. Step 4

The mixture obtained from step 3 is cooled to room temperature (at about 25 °C - 30 °C) and the resulting mixture is poured into water and filtered. This is done to remove unused potassium carbonate and other salts such as potassium bromide.

The precipitate obtained is washed with methanol and dichloromethane (about 5 ml- 50 ml of each solvent used). The washing is carried out in each solvent for 1-15 minutes and the resulting mixture is dried in vacuum at a temperature of 50-60 °C. Step 5

The precipitate is further purified by soxhlet extractions with methanol, dichloromethane, toluene and tetrahydrofuran (about 5 ml-50 ml of each solvent used). The purification is carried out in each solvent for 3 hours- 15 hours to give the product as a dark green solid ( 100-200 mg). This step ensures that there are no soluble monomers and oligomers, in the desired final product.

The mechanism of the Suzuki reaction is best viewed from the perspective of the palladium catalyst. The first step is the oxidative addition of palladium to the bromide of TBP to form the organopalladium species. Reaction with base Potassium carbonate (K ₂ CO ₃ ) gives an intermediate, which via transmetalation with the boron-ate (BDBA) complex forms the organopalladium species. Reductive elimination restores the original palladium catalyst leading to the desired monomers. Repetition of the above steps leads to the super absorbent micro porous polymer (Py-PP). Example 2

Physical characterization of Py-PP polymer

The synthesized polymer is characterized substantially using various methods.

In an embodiment, the Solid-state NMR of Py-PP (50-100 mg) show three peaks at 139.5, 136.2, and 126.7 ppm corresponding to the 3 types of un-substituted and substituted phenyl carbon atoms, respectively as marked in the figure 3.

The structure of Py-PP is also evident from the solid-state FT-IR measurements of Py- PP (0.1-0.5 mg) [figure 4; FT-IR (v; cm ^"1 ): 3325, 3060, 3010, 1595, 1480,1450,1390,1175,1051, 1004, 834, 702], which show signals corresponding to aromatic C=C stretch (1595 cm ^"1 ), C=C vibrational modes of the substituted phenyl rings (1480 and 1450 cm-1) and aromatic C-H stretch (3060-3010 cm ^"1 ). In addition, IR signals corresponding to trace amounts of the end functional B(OH) ₂ or OH groups (3300 cm ^"1 ) corresponding to BDBA and C-Br (1005cm ¹ ) corresponding to TBP are also observed which completely gets disappeared in the Py-PP spectrum due to the formation of polymer network.

In an embodiment, the powder X-ray diffraction (PXRD) pattern of Py-PP has been provided in figure 5. The PXRD pattern of Py-PP shows the absence of any diffraction peaks indicating the amorphous nature of Py-PP polymer.

In another embodiment, the EDX analysis and SEM image of Py-PP is depicted in figure 6. Based on the EDX analysis, the elemental Analysis (%) is calculated for C ₂₈ Hi ₄ : C= 95.617, H= 4.383 and is found to be: C= 86.72; H= 4.34. In an embodiment, the emission spectra of Py-PP (5-10 mg) measured with Perkin Elmer Ls55 Luminescence Spectrometer shows a greenish yellow emission (500-700 nm) with maximum at 540 nm [figure 1 (c)]. The red-shifted absorption (374 nm) and emission (540 nm) of Py-PP compared to tetraphenyl pyrene (λ^ = 320 nm and λειη = 450 nm) indicates the presence of extended conjugation in the polymer. The results of absorption and emission spectra are also provided in figure 7. These results indicate that the Py-PP polymer has an absorbance range (UV-Vis) of about 300-500 nm and emission range of about 500-700 nm and thus the polymer combines both the microporous and luminescent functionalities, consistent with its design. In another embodiment, the thermogravimetric analysis (TGA) of Py-PP (5-10 mg) shows excellent network stability up to 500 °C and only 5 to 7% weight loss is observed at the initial stages (ca. 200 °C), which is probably due to trapped solvent molecules. Figure 8 illustrates the TGA profile of Py-PP measured under N ₂ atmosphere.

N ₂ adsorption study of the degassed samples of about 150 mg of Py-PP degassed at 210°C for a period of 18 hours under high vacuum (10 ¹ pa), are carried out using QUANTACHROME QUADRAS ORB -SI analyzer at 77 K . The adsorbates are charged into the sample tube, and then the change of the pressure is monitored. The degree of adsorption is determined by the decrease of the pressure at the equilibrium state. All operations are computer-controlled and automatic. N ₂ gas adsorption experiments (77 K) of the polymer, desolvated at 483 K, shows a typical type I isotherm profile, with steep uptake at low pressure [figure 1 (b)], which indicates the microporous nature of the network, with a maximum N ₂ uptake of 792 mLg ¹ . The increase in N ₂ uptake at P/Po>0.8 in the adsorption isotherm is attributed to the interparticulate porosity associated with the meso and macrostructures of the sample in the bulk. Further, the BET (Brunauer-Emmett-Teller) surface area is evaluated to

Example 3

Functional Characterization of Py-PP polymer

The adsorption studies with toluene and water vapors (Figure 9a) provide insights into the dynamic nature and polarity of Py-PP networks. Though, the adsorption profiles show significant uptake for toluene vapors (240 mL/g), the pores are not accessible to water vapors (typical type II profile), which is consistent with the hydrophobic nature of the polymer. The adsorption isotherm of toluene displays a rapid uptake at low relative pressures (P/Po ~ 0.2) followed by a monotonically increasing profile with the increase of pressure, which end without saturation at P/P ₀ ~ 1 , indicating a structural transformation with gradual unfolding of the porous network. Furthermore, desorption isotherm does not retrace the adsorption resulting in a large hysteresis. The incomplete desorption and large hysteresis showcases strong interaction of the toluene molecules with the pore surface and solvent-induced structural modification, thus unveiling the dynamic and soft characteristics of Py-PP. The Py-PP exhibits enhanced green fluorescence with various organic solvents, reiterating the guest induced structural changes in its conjugated backbone (Figure 9b) and hence its emission properties to further probe the dynamic nature of the network is used. In order to investigate this property, the desolvated Py-PP is exposed to various organic solvents and then the emission spectra are recorded. In a typical experimental procedure, 20 mg of desolvated polymer is soaked in 1 mL of various anhydrous solvents for 5 minutes. The wet powder is then purged with nitrogen gas to ensure the removal of physically absorbed solvent molecules and finally the resultant powder sample is analyzed using a front-face fluorescent spectrometry set-up ( exc = 380 nm). Solvent exposed powders of Py-PP shows visible color changes from yellowish green to bright green and an enhancement in fluorescence intensity with varying orders of magnitude depending on the solvent (Figure 9b ). The emission spectra of the solvent-exposed polymers (-525 nm) shows a blue-shift with respect to the desolvated Py-PP (540 nm). The maximum fluorescence enhancement is observed for aromatic non-polar solvent like o-dichlorobenzene (ODCB, 4-5 times) whereas the polar solvents like DMF and ethanol show only 1.5-2 times enhancement in the emission. Py-PP, does not show any fluorescence response with water, proving further the hydrophobic interior of the polymer. This guest-responsive emission is attributed to the structural reorganization in the framework due to reduced inter-molecular interactions induced by the hydrophobic solvent molecules. Time-resolved decay emission measurements further proves the changes in local environment of pyrene chromophores on expansion of the network with guest molecules (Figure 9c). The decay profiles are best fitted by a tri-exponential function and significant increase in the life -time is observed with non-polar solvents (eg. for toluene 0.1 , 1.0 and 2.97 ns) which is consistent with the increase in emission intensity, compared to that of desolvated Py-PP (0.07, 0.48, and 1.7 ns). However, no significant changes in lifetimes are observed with polar solvents like DMF and ethanol (Figure 9c). Time dependent steady-state fluorescence measurements of solvent exposed Py-PP shows that the emission maxima slowly (within 1 hour for toluene) shifts back to the red- shifted emission of desolvated framework clearly suggesting the reversibility of guest- induced breathing of the Py-PP framework (Figure 9d). In another embodiment, the results of fluorescence response and Picosecond life time studies are further provided in table 1 and table 2 respectively.

Table 1 : Fluorescence response data of Py-PP with different organic solvents

Table 2: Picosecond life time data of Py-PP alone and with different organic guests

The amorphous and dynamic porous features of the Py-PP is further used to investigate the absorbent behaviour with solvent/guest molecules. The Py-PP exhibits remarkable solvent uptake and resultant swelling in presence of various organic solvents. In addition, the solvent uptake is accompanied by a simultaneous increase in fluorescence of the framework, suggesting the crucial role of flexible backbone in the swelling process. The absorbent properties of Py-PP with various organic solvents has been investigated and systematic study of the swelling behaviour of Py-PP in various organic solvents, petroleum products and ethanol in terms of their equilibrium state of swelling parameter (Q%) (Figure 10) and equilibrium solvent content (H%) has been carried out. The swelling parameters of Py-PP are summarized in Figure 10. The results showcase that Py-PP is a superabsorbent.

In an embodiment, the phase-selective swelling of few hydrocarbon solvents are represented in figures 12, 13, 14. Figure 11 shows the SEM image of Py-PP gel in ODCB. Figure 12 shows the photograph of swelled sample of Py-PP (20 wt%) in toluene indicating no release of solvent after swelling under STP Figure 13 depicts the swelled sample of Py-PP (20 wt%) in CHC1 ₃ a) under normal day light and b) under UV-light, which shows visible volume increase and enhanced blue shifted emission up on swelling in CHCI ₃ and there is no release of solvent under STP.

In another embodiment of the present disclosure, due to the electron-rich and curved p surface of Py-PP porous backbones, the encapsulation of convex fullerene (C ₆ o), a polycyclic aromatic hydrocarbon (PAH) which is a known electron-acceptor molecule is also investigated. The Py-PP is soaked in a pale purple, saturated toluene solution (~ 2.7 mM) of C ₆ o and the solution almost immediately (<1 min) turns colourless, which showcases the efficient and instantaneous encapsulation of C ₆ o molecules inside the porous network (Figure 14a). This is further evident from the lack of any fullerene absorption bands in the UV spectra of residual solution. This process is repeated three to four times with the same polymer sample to finally obtain a 15 wt% (with respect to the polymer weight) encapsulation of C ₆ o. The recovery of the polymer and C ₆ o are 100 %. Definitive proof for the C ₆ o encapsulation is provided by N ₂ adsorption measurements of desolvated Py-PP-C ₆ o adducts, which shows a 20% decrease in the BET surface area compared with pure Py-PP without guest molecules (Figure 14b). The corresponding pore volume decreases from 0.71 cm ³ g ^_1 of as synthesised desolvated Py-PP to 0.54 cm ³ g ^_1 in Py-PP-C ₆ o adducts. The fluorescence of the fullerene-encapsulating Py-PP is completely quenched with no evidence for ground-state charge-transfer interactions, which proves the excited state electron/energy transfer process from pyrene to the C ₆ o (Figure 14c). This is further evident from the quenching of fluorescence lifetime of the pyrene donor in the presence of the C ₆ o (Figure 14d). Preliminary nanosecond laser flash photolysis studies on Py-PP-C ₆ o dispersion shows the presence of the pyrene radical cation at λ=490 nm (figure 15), which indicates photo-induced electron transfer from the framework to the encapsulated guest C ₆ o molecules. Furthermore, the encapsulation of C ₆ o allows the formation of gels with only 5 wt% Py-PP in toluene upon sonication (figure 16), compared to 20 wt% of polymer required for gelation in the absence of fullerene guests. The picosecond life time study of Py-PP with and without C ₆ o is further provided in table 3.

Table 3: Picosecond life time data of Py-PP with and without C^n

In another embodiment, the removal of fullerene and Nile red (NR) Dye [aromatic pollutant] from toluene is also tested. The amount of NR uptake is shown to be 10 wt% and recovery of the polymer and NR is 100 %.

In another embodiment, the Py-PP polymer of the present disclosure works efficiently over a broad range of temperatures ranging from about 0 °C to about 550 °C. The Py- PP polymer is further resistant towards acidic, basic and salty conditions.

Example 4

Quantitative Analysis of detection, removal and recovery of VOCs, PAHs and aromatic pollutants by employing Py-PP polymer

The Py-PP polymer of the instant disclosure is used successfully for sensitively detecting, removing and recovering various VOCs, PAHs and aromatic pollutants. The absorbent properties of Py-PP with various VOCs, PAHs and aromatic pollutants has been investigated and a systematic study of the swelling behaviour of Py-PP in terms of their equilibrium state of swelling parameter (Q%) and equilibrium solvent content (H%) has been calculated from the weight of dried and swollen polymers using the following equation- H - ⁽ W _we , - W _diy )/W _wet X 100

Q = W _wet / _d:ry X 100

Where, Q= equilibrium state of swelling parameter

H= equilibrium solvent content

weight of the polymer before absorbing

weight of the polymet after absorbing with solvents

The results of various organic guests sensitively detected, removed and recovered are provided in Table 3. Table 3 : H and Q data of Py-PP with different organic solvents.

Further, the removal of fullerene (C ₆ o) from toluene has also been tested. The amount of C ₆ o uptake is 15 wt% (with respect to the weight of Py-PP) and recovery of Py-PP polymer and C ₆ o are 100 %.

In addition, the removal of fullerene Nile red (NR) Dye from toluene is also tested. The amount of NR uptake is 10 wt% (with respect to the weight of Py-PP) and recovery of the Py-PP polymer and NR are 100 %. As it is observed from Table 3, the swelling parameter and the solvent content vary between 900-1950 and 90-99 respectively, for various organic solvents under investigation proving that Py-PP is a superabsorbent. Starting from the nonpolar hexane, the swelling degree increases with increasing solvent polarity, and the maximum swelling is observed for ODCB. For example, Py-PP immobilizes ODCB to roughly 20 times to its own native weight. Then, the swelling degree decreases with increasing solvent polarity and the polymer does not swell with water, which is consistent with the hydrophobic aromatic framework structure of Py-PP. Noticeably, the swelling process is instantaneous when compared to classical polymer absorbents and is stable for months. In an embodiment, the time taken for swelling of the Py-PP of the present disclosure is less than a minute. In a preferred embodiment, the time taken is about 5-10 seconds. Furthermore, this process is repeated many times using recycled Py-PP after the desolvation process under vacuum. In addition, it is observed that the swelling process is more efficient while sonication or stirring and green fluorescent gel-like, self-standing materials are formed within seconds, with only 4 wt% of Py-PP with ODCB. Although the micropores of Py-PP are robust for the diffusion of small gas molecules (vide supra), solvation results in the structural reorganization of the aromatic framework, resulting in the observed macroscopic swelling. This instantaneous swelling and fluorescence signalling are hitherto unknown features in microporous polymers and therefore, the Py-PP of the instant disclosure is exploited as selective absorbent and sensory materials.

Recovery Process: 60% of VOCs are recovered by simple squeezing and 100% recovery is achieved through distillation. In case of PAHs and aromatic pollutants, the Py-PP is washed with the solvent where corresponding PAH or aromatic pollutant is soluble. By evaporating these solutions, PAH or aromatic pollutant are recovered. After this process, the Py-PP is dried in vacuum and reused several times. Example 5

Reusability of Py-PP

The Py-PP polymer of the present disclosure is re-used several times and the efficiency of Py-PP polymer remains significantly unaffected when reused up to a number of cycles. Since all the VOCs, PAHs and aromatic pollutants interact non- covalently with Py-PP and does not account to any chemical damage to the structure, the Py-PP retains its characteristics (as confirmed by Uv-Vis, Fluorescence, Surface area and TGA measurements provided in the above examples) and is therefore ready for reusability.

A specific example to showcase the feature of reusability of Py-PP has been provided in Table -4.

Table 4: Efficiency of VOC uptake by Py-PP polymer when re -used up to 20 cycles

CYCLE NO. Weight of Py-PP EFFICIENCY OF

VOC (Chloroform)

UPTAKE (at 30 °C)

1 30 mg 94 %

2 30 mg 93 %

3 30 mg 93.5 %

4 30 mg 94 %

5 30 mg 94.5 %

6 30 mg 94.3 %

7 30 mg 93.8 %

8 30 mg 92.5 %

9 30 mg 93.1 %

10 30 mg 94.2 %

11 30 mg 93.5 %

12 30 mg 92.5 %

13 30 mg 93.5%

14 30 mg 92.8 % 15 30 mg 93.7 %

16 30 mg 94.3 %

17 30 mg 93.6 %

18 30 mg 94.1 %

19 30 mg 93.5 %

20 30 mg 92.8 %

As observed from Table 4, the efficiency of Py-PP is significantly unaffected when the Py-PP is reused up to 20 cycles. Example 6

Comparative study of Py-PP with currently available absorbent material

Table 5 provides a comparative data showcasing the advantages of the Py-PP polymer of the present disclosure with respect to the currently available absorbent materials.

Absorbent Stability Large Scale Production Recovery Material

Organo gels < 100 °C Difficult Expensive

[involves multi step synthesis [always thermal and enhances the cost for distillation is required large scale production; the for recovery of the material works only in VOCs; PAHs and confined environment which organic pollutants keeps them way from cannot be removed or practical applications] recovered because of high boiling temperature of these materials which decomposes the gels;

Simple squeezing techniques cannot be applied for recovery due to low mechanical stability of the organo gels]

Carbon >500 °C Difficult and non fluorescent Expensive

Nanomaterials

[synthesis requires use of [the recyclability and

(RECAM®)

very expensive instruments speed of uptake of these and requires high materials is not as temperatures (600-1000 °C) efficient as the Py-PP which result in very polymer of the present expensive products; disclosure; since they fluorescence based are very light and toxic techniques cannot be to the environment, their employed for detection] disposal after usage is also a big concern]

Hydrophobic <400 °C Difficult, highly dense Expensive

Clays materials and non fiuorescent

[release of absorbed

[as synthesized clay materials material is not very are hydrophilic and efficient mainly because converting these hydrophilic of rigid structure of the clays into organophilic clays clays] is an expensive and tedious

procedure; since these clays

are composed of metal ions,

their density is high;

fluorescence based

techniques cannot be

employed for detection]

Inorganic >500 °C Difficult and non fluorescent Expensive nanowires [synthesized using [Release of absorbed hydrothermal and high material is not very temperature furnace based efficient]

methods which are

expensive; fluorescence

based techniques cannot be

employed for detection]

Silicone <200 °C Difficult and non fluorescent Expensive sponges

[synthesized using freeze

(Nanogel@aer

drying and other

ogel,

polymerization methods

Maerogel)

which are expensive; they

have low thermal stability;

fluorescence based

techniques cannot be

employed for detection]

Py-PP >500 °C Easy Inexpensive

As observed from the above table, the Py-PP material of the present disclosure is superior in all the aspects such as stability, large scale production and cost when compared with the known materials.

The superabsorbent Py-PP polymer of the present disclosure can be employed as routine industrial method to save human life and to prevent environment damage in all areas where organic conjugated-superabsorbent finds applications such as VOCs, PAHs, aromatic pollutants detection and removal.

In conclusion, the present disclosure introduces a multi-functional organic microporous polymer (Py-PP) in which the porous fluorescent frameworks undergo swelling in the presence of hydrophobic and aromatic guests. This remarkable guest- induced breathing of the hydrophobic pores imparts unprecedented properties, such as super-absorbency and phase-selective removal of various VOCs, PAHs and aromatic pollutants, for this soft microporous organic polymer. Thus, the fluorescent and electron-donating pyrene scaffold combined with dynamic porosity of the Py-PP polymer is exploited for the applications of detection, removal and recovery of various organic compounds.