Isoporous membrane and process for preparation thereof

Abstract

The present invention provides a thin film of formula 1 Q14H22[K4P8W48O184].12H 2 O for membrane-based separation. The invention relates to the development of well-defined, iso- porous membranes for molecular separation. A key challenge in this field has been creating defect-free films with crystalline iso-pores, particularly using porous polyoxometalates (POMs). The present invention overcomes this challenge by assembling 1 nm pores of POMs into a mechanically robust, continuous thin film through a short-chain molecular entanglement approach. The resulting isoporous film exhibits high crystallinity, flexibility, tunable thickness ranging from (>30 nm), and large lateral dimensions (50 cm²). This innovative film demonstrates significant mechanical strength and efficiently separates molecules larger than 1 nm² (Molecular dimension). The separation efficiency is enhanced by the well-ordered pores, which minimize pore size distribution.

Description

[0001] P_IN1005500

[0002] ISOPOROUS MEMBRANE AND PROCESS FOR PREPARATION THEREOF FIELD OF THE INVENTION

[0003] The present invention relates to isoporous membranes and process for preparation of crystalline isoporous membranes with a well-defined isoporous, active separation layer, particularly nanofiltration membrane with chemical formula 1 Qi4H22[K4PsW4sOi84].12H2O, designed for accurate molecular separation. More specifically, the present invention encompasses the fabrication of an isoporous membrane using intrinsically porous materials having chemical formula 1 Qi4H22[K4PsW48Oi84].12H2O, wherein Q is quaternary ammonium salts (NR4+), wherein R is an alkyl group consisting of C4 -C10 carbon chain. Further, isoporous membrane is coated onto an ultrafiltration support for membrane-based separation in aqueous systems.

[0004] BACKGROUND AND PRIOR ART OF THE INVENTION

[0005] Membrane technology provides a scalable, eco-friendly, and energy-efficient method for separating small chemical, pharmaceutical, and biological molecules with molecular dimension ranging from approximately 0.5 to 5 nm2in size having molecular weight ranging from 200-2000 Dalton. However, the separation of organic molecules with dimensions of 1 -3 nm2having molecular weight 300-600 Dalton, remains a challenging and underexplored area. Many emerging contaminants of environmental concern, such as plastic additives, pesticides, textile dyes, and pharmaceutical pollutants, fall within this size range and are notoriously difficult to remove from wastewater streams. These applications led to address the solution of many urgent societally relevant issues of clean water and air, public health, climate change, waste minimization, and energy production.

[0006] Accurate molecular separation, defined by separation selectivity of molecules (Molecular dimensions of 1-3 nm2having molecular weight 300-600 Dalton) is indispensable in various industrial processes for achieving product purity, process efficiency, and environmental sustainability. It is one of the major challenges of membrane-based separations that relates to the pore structure of the membranes but is rarely addressed. Accurate molecular separation is the key to highlight of recent research in the field of non-energy-intensive membrane-based separation, to produce and recover high-quality or valuable products by minimizing waste.P_IN1005500

[0007] Polymers have been the primary materials used in membrane fabrication due to their flexibility, mechanical robustness, and ease of processing. However, polymeric membranes often exhibit amorphous structures with limited pore tunability and broad pore size distributions. To address these limitations, there is a strong demand for membranes with fixed pore size and low pore size distribution. Industrial applications require membranes with stable separating layers that offer both molecular selectivity and high permeance. While high permeance can be achieved by reducing the thickness of the separating layer, this often introduces defects that hinder scalability. To achieve accurate molecular separation, membranes with well-defined pores of sub-nanometer size and stable, permanent porosity are highly desirable. In polymeric membranes, sub-nanometer pores are typically formed by inefficient packing of polymer chains, leading to interconnected voids. However, these pores are prone to collapse over time due to polymer relaxation, aging, fouling, and other factors, resulting in a loss of selectivity.

[0008] The fabrication of isoporous (Uniform pores) membranes addresses these challenges by incorporating materials with pre-defined, permanent crystalline pores in an ordered arrangement, show high separation selectivity of molecules (With molecular dimensions of 1-3 nm2having molecular weight 300-600 Dalton). Materials such as metal-organic frameworks (MOFs), covalent organic frameworks (COFs), hydrogen-bonded organic frameworks (HOFs), porous organic cages (POCs), porous aromatic frameworks (PAFs), and porous molecular crystals (POC), along with self-assembled materials like polyoxometalates (POMs), provide the basis for constructing isoporous membranes. The key elements for fabricating high-performance isoporous membranes include: (i) the use of complementary materials with ordered, pre-defined pores; (ii) homogeneous distribution of porosity throughout the membrane; (iii) the production of defect-free membranes over large areas; and (iv) ensuring good mechanical strength for industrial applicability. These advancements in isoporous membrane fabrication offer a promising solution for high-flux, precise molecular separations, making significant contributions to various industrial processes and societal needs

[0009] Reference may be made to US2024 / 0058767A1, wherein method of synthesizing selfassembled reaction between glycerol and cationic surfactant led to the preparation of hexagonal arrayed of uniform pores with Inm2dimension disclosed. The claimed membrane shows lowP_IN1005500

[0010] solute separation selectivity (-4) for molecules with molecules with dimensions of 1-3 nm2having molecular weight 300-600 Dalton.

[0011] Reference may be made to an article published in Journal of American Chemicals Society, 139, 2017, 13083 by Banerjee, wherein interfacial synthesis to produce COF thin film (Pore size from 1.4 to 2.3 nm) for the molecular separation reported. The reported approach is limited by long reaction time, low lateral size, and batch type separation via adsorption mechanism not true membrane -based separation with high mass transport. The formed COF based membrane show low solute separation selectivity (-1.33) for molecules with molecules with dimensions of 1-3 nm2having molecular weight 300-600 Dalton.

[0012] Reference may be made to an article published in Nature Communications, 9, 2018, 2294 by Kumar and his coworkers, wherein the polymer membranes with well-defined, densely packed artificial water channels, made up of peptide-appended pillar arene (PAP) artificial water channel with a pore size of 0.5 nm disclosed. The disclosed membrane showed low solute separation selectivity (-2.5) for molecules with molecules with dimensions of 1-3 nm2having molecular weight 300-600 Dalton.

[0013] Reference may be made to an article published in Nature Materials, 21, 2022,463 by Cooper and his coworkers, wherein they used interfacial crystallization approach to prepare crystalline thin film made of intrinsic pores. These pores are connected via hydrophobic -hydrophobic interaction. The formed crystalline porous organic crystalline thin film membrane shows low solute separation selectivity (-1.8) for molecules with molecules with dimensions of 1-3 nm2having molecular weight 300-600 Dalton.

[0014] Reference may be made to an article published in Advance Functional Material, 34, 2024, 2312203 by Liu and his coworkers, wherein they prepared mixed matrix membranes made up of step -wise preparation. Firstly, thin films of COF membrane prepared using interfacial synthesis, followed by crystallization of MOF into the pores of COF. This approach resulted into the formation of membrane with uniform pores (-1.1 nm2). The claimed membrane shows low solute separation selectivity (-1.2) for molecules with molecules with dimensions of 1-3 nm2having molecular weight 300-600 Dalton.P_IN1005500

[0015] Reference may be made to Chinese patent CN117379989, wherein composite film is characterized by comprising a base material and a functional layer deposited on the base material, wherein the functional layer is a heteropolyacid molecular cluster intercalated reduced graphene oxide layer. Preferably, the heteropolyacid molecular cluster is selected from at least one of phosphotungstic acid, phosphomolybdic acid, silicotungstic acid and borotungstic acid. The membranes exhibited high NaCl retention rates (up to 99.5%) and high-water flux, showing their effectiveness for desalination processes. The water flux ranged from 157.19 mol / m2 / h, with high salt rejection (R) values. The membrane has high stability, uniform size, good longterm stability (over 400 hours).

[0016] Reference may be made to an article published in Journal of American Chemicals Society, 146, 2024, 2313 by Khasab and his coworkers, wherein they have prepared two dimensional ionic COF with uniform pore size of 1.4 nm using sequential casting reaction in 48 hours. The formed COF based membrane show low solute separation selectivity (~6) for molecules with molecules with dimensions of 1-3 nm2having molecular weight 300-600 Dalton.

[0017] Reference may be made to European patent EP2063980B1, wherein a process for the preparation of an isoporous integral-asymmetric polymer membrane, namely an ultrafiltration membrane or nanofiltration membrane was reported. An isoporous integrally asymmetric polymer membrane prepared by this process and the use of such an isophoric integrally asymmetric polymer membrane for ultrafiltration or nanofiltration. The at least one block copolymer comprises a structure of the form AB or ABA or ABC, where A or B or C are each polystyrene, poly-4-vinylpyridine, poly-2-vinylpyridine, polybutadiene, polyisoprene, poly (ethylene-stat -butylene), poly (ethylene-alt-propylene), polysiloxane, polyalkyleneoxide, poly-s-caprolactone, polylactide, polyalkylmethacrylate, polymethacrylic acid, polyalkylacrylate, polyacrylic acid, polyhydroxyethylmethacrylate, polyacrylamide or poly-N-alkylacrylamide. The density of surface pores in the membrane is at least 108 pores / cm2.

[0018] Reference may be made to European patent EP2695669B1, wherein method for producing a polymer membrane having an isoporous separation-active layer, in particular an ultrafiltration membrane or nanofiltration membrane claimed, wherein the at least one block copolymer comprises two or three different polymer blocks A, B and, if applicable, C of the configurationP_IN1005500

[0019] A-B, A-B-A or A-B-C, wherein the polymer blocks are selected from the group of polystyrene, poly-4-vinylpyridine, poly-2-vinylpyridine, polybutadiene, polyisoprene, poly(ethylene-stat-butylene), poly(ethylene-alt-propylene), polysiloxane, polyalkylene oxide, poly-s-caprolactone, polylactide, polyalkylmethacrylate, polymethacrylic acid, polyalkylacrylate, polyacrylic acid, polyhydroxymethacrylate, polyacrylamide, poly-N-alkylacrylamide, polysulfone, polyaniline, polypyrrole, polytriazole, polyvinylimidazole, polytetrazole, polyethylene diamine, polyvinyl alcohol, polyvinylpyrrolidone, polyoxadiazole, polyvinyl sulphonic acid, polyvinyl phosphonic acid or polymers with quaternary ammonium groups. The block copolymer has a molecular weight between 100 kDa and 600 kDa, in particular between 130 kDa and 250 kDa.

[0020] In light of the above, it is realized that no single prior art discloses quaternary ammonium salt functionalized isoporous polyoxometalate membrane, and its fabrication by short-chain molecular entanglement approach. Thus, keeping in view the drawbacks of the hitherto reported prior arts, there are still opportunities to process for preparation of well-defined isoporous membrane for accurate molecular separation, effectively targeting molecules larger than 1 nm2(Stokes radii), with reduced pore size distribution.

[0021] In view of the above and obviate the drawbacks of existing prior arts, present invention relates to isoporous membranes and process for preparation of crystalline isoporous membranes (Inm2) ) with a well-defined isoporous, active separation layer, particularly nanofiltration membrane with chemical formula 1 Qi4H22[K4P8W4sOi84].12H2O, designed for accurate molecular separation The nanofiltration membrane with chemical formula 1 Qi4H22[K4P8W4sOi84].12H2O, having high crystallinity, flexibility, tunable thickness (>30 nm) and large lateral size (50 cm2). Short chain molecular entanglement approach was used to selfassembled 1 nm size pores of polyoxometalates to form defect free continuous thin film. The resulting isoporous thin membrane showed substantially higher mechanical strength and separates the molecules above the size of 1 nm2(Molecular dimension). The prepared membranes show high solute separation selectivity for molecules with molecular dimensions of 1-3 nm2having molecular weight 300-600 Dalton.P_IN1005500

[0022] OBJECTS OF THE INVENTION

[0023] The main objective of the present invention is to provide a functionalized isoporous polyoxometalates membrane of formula 1 Qi4H22[K4P8W48Oi84].12H2O.

[0024] Another objective of the present invention is to process for the preparation of functionalized isoporous polyoxometalates of formula 1 Qi4H22[K4PsW48Oi84].12H2O.

[0025] Another objective of the present invention is to prepare the thin film of functionalized isoporous polyoxometalates of formula 1 Q P ! K4PP 48O 184] .I2H2O .

[0026] Another objective of the present invention is to coating the thin film of functionalized isoporous polyoxometalates on ultafiltration support to prepare the thin film composite (TFC) membrane with formula 1 Qi4H22[K4P8W48Oi84]-12H2O for the selective separation in aqueous system via cross -flow filtration assembly.

[0027] Another objective of the present invention is to increase the solute separation selectivity for molecules with molecules with dimensions of 1-3 nm2having molecular weight 300-600 Dalton.

[0028] Another objective of the present invention is to reuse the thin film composite (TFC) membrane with formula 1 Qi4H22[K4P8W48Oi84]-12H2O after washing with deionized water, selectivity remains as such.

[0029] SUMMARY OF THE INVENTION

[0030] Additional features and embodiments of the present disclosure will be better understood through the techniques and other aspects of the disclosure. Other embodiments of the invention are described in detail herein and are considered a part of the claimed disclosure.

[0031] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description section. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.P_IN1005500

[0032] The following is a condensed description of the disclosure to give the reader with a basic understanding. Its main goal is to present some of the principles described in this document in a simpler version as a prologue to the more extensive exposition that follows.

[0033] The present invention, and in accordance with main aspect of the present invention relates to isoporous membranes and process for preparation of crystalline isoporous membranes with a well-defined isoporous, active separation layer, particularly nanofiltration membrane with chemical formula 1 Qi4H22[K4P8W4sOi84].12H2O, designed for accurate molecular separation. More specifically, the present invention encompasses the fabrication of an isoporous membrane using intrinsically porous materials having chemical formula 1 Qi4H22[K4PsW48Oi84].12H2O, wherein Q is quaternary ammonium salts (NR4+), R is hydrocarbon containing group selected from the group consisting of [C4 to C10] alkyl. Further, isoporous membrane is coated onto an ultrafiltration support for membrane -based separation in aqueous systems.

[0034] Accordingly, the present invention provides an isoporous free-standing thin film membrane of functionalized isoporous polyoxometalate with formula 1

[0035] Q14H22[K4P8W48O184].12H2O.

[0036] Formula 1

[0037] Wherein Q is quaternary ammonium salts (NR4+), where R is hydrocarbon containing group selected from the group consisting of [C4 to C10] carbon chain.

[0038] In aspect of the present invention, a thin film composite (TFC) isoporous membrane comprises:

[0039] a) a thin film of functionalized isoporous polyoxometalates of formula 1 [Qi4 H22 [K4P8W48O184] .I2H2O], wherein Q is quaternary ammonium salts (NR4+), R is an alkyl group consisting of C4 -C10 chain;

[0040] b) an ultrafiltration support.

[0041] In aspect of the present invention, wherein compound of formula 1 is selected from tridecatetrabutyl ammonium tetra potassium octatetracontatugsto(VI) octaphosphate(V)P_IN1005500

[0042] (Pl QI), tridecatetrahexylammonium tetra potassium octatetracontatugsto(VI) octaphosphate(V) (P1Q2), tridecatetraheptylammonium tetra potassium octatetracontatugsto(VI) octaphosphate(V) (P1Q3), tetradecatetrakis(decyl)ammonium tetra potassium octatetracontatugsto (VI) octaphosphate(V) (P1Q4).

[0043] In aspect of the present invention, wherein R is alkyl group selected from the group consisting of tetrabutyl, tetrahexyl, tetraheptyl or tetradecyl.

[0044] In aspect of the present invention, wherein quaternary ammonium salts (NRV) in compound of formula 1 is selected from Tetrabutyl ammonium bromide, Tridecatetrahexylammonium bromide, Tridecatetraheptylammonium bromide and Tetradecatetrakis(decyl)ammonium bromide.

[0045] In aspect of the present invention, wherein ultrafiltration support selected from poly ether sulphone (PES) or polyacrylonitrile (PAN).

[0046] In aspect of the present invention, wherein process for the preparation of thin film membrane of functionalized isoporous polyoxometalates of formula 1 Q14 H22 [K4P8W48O184] .I2H2O via cation exchange strategy comprising the steps of:

[0047] a) dissolving dicontaoctapotassium pentalithium octatetracontatugsto(VI) octaphosphate(V) (Pl) in DI water (solution A);

[0048] b) dissolving tetraalkyl ammonium bromide (Q) in polar aprotic or nonpolar solvent or mixture of polar aprotic and nonpolar solvent (solution B);

[0049] c) adding solution, A in solution B and stirred continuously in the range of 800-1200 rpm at temperature in the range of 25 °C to 30 °C for a time period in the range of 4-24 hrs to obtain biphasic solution;

[0050] d) separating the biphasic solution obtained in step (c), followed by evaporation of organic solvent led to the solid or highly viscous material;

[0051] e) dissolving viscous material obtained in step (d) in hexane and dispersing on the deionized (DI) water bowl to form freestanding isoporous film (TFP1Q2);

[0052] f) transferring isoporous film (TFP1Q2) onto the ultrafiltration support to obtain thin film composite (TFC) membrane;P_IN1005500

[0053] g) washing the thin film composite (TFC) membrane with water and dried at temperature in the range of 25-30 °C for the time range of 24-30 hours, followed by curing at temperature in the range of 5-10°C in water for time period in the range of 4-5 hours.

[0054] In aspect of the present invention, wherein the tetra alkyl ammonium bromide is selected from the group consisting of tetrabutyl ammonium bromide, tetrahexyl ammonium bromide, tetraheptyl ammonium bromide and tetradecyl ammonium bromide.

[0055] In another aspect of the present invention, wherein the polar solvent is selected from water, methanol or acetonitrile.

[0056] In another aspect of the present invention, wherein nonpolar solvent is selected from toluene, xylene, hexane or heptane.

[0057] In another aspect of the present invention, wherein tetraalkyl ammonium bromide in polar aprotic or nonpolar solvent or mixture of polar aprotic and nonpolar solvent in the ratio of 1 : 1 (v / v) wherein the ratio of tetraalkyl ammonium bromide and solvent is in the ratio of 0.002: 1: 1 (w:v:v)

[0058] BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1: FT-IR spectra of P1Q1.

[0059] FIG. 2: FT-IR spectra of P1Q2.

[0060] FIG. 3: FT-IR spectra of P1Q3.

[0061] FIG. 4: FT-IR spectra of P1Q4.

[0062] FIG. 5: TGA analysis of PIQn.

[0063] FIG. 6: Scanning electron microscopy for thin films of functionalized porous Pl (PIQn).

[0064] FIG. 7: Transmission Electron Microscopy for thin film of functionalized porous Pl (PIQn).P_IN1005500

[0065] FIG. 8: Separation performance of cationic, anionic & neutral molecular markers for thin film of functionalized porous Pl(PlQn).

[0066] FIG. 9: Separation performance of P1Q1 to P1Q4 for 24 hours using anionic, neutral & cationic molecular markers.

[0067] FIG. 10: Selectivity of P1Q1 to P1Q4 membranes.

[0068] FIG. 11: (a) Synthesis of functionalized porous polyoxometalate P 1 Q 1 and thin film of P 1 Q 1 ; (b) Synthesis of functionalized porous polyoxometalate P1Q2 and thin film of P1Q2; (c) Synthesis of functionalized porous polyoxometalate P1Q3 and thin film of P1Q3; (d) Synthesis of functionalized porous polyoxometalate P1Q2 and thin film of P1Q2.

[0069] DETAIL DESCRIPTION OF THE INVENTION

[0070] The following description is not to be taken in a limiting sense but is given solely for the purpose of describing the broad principles of the invention. Embodiments of the invention will be described by way of example, with reference to the above-mentioned drawings showing elements and results according to the present invention.

[0071] The foregoing detailed description of the disclosure is elaborated to provide a clear understanding to the person who is skilled in the art. Additional features, embodiments and advantages of the invention will be described hereinafter which forms the subject of the claims of the disclosure, However, the set forth disclosure provided in the specification will best be understood in conjunction with the appended claims and FIG.s as provided heretofore. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure. It should also be realized by those skilled in the art that such equivalent processes do not depart from the spirit and scope of the disclosure as set forth in the appended claims. It will be readily understood that the aspects of the present disclosure, as generally described herein, illustrated in the FIG.s, and can be arranged, substituted, combined, and designed in various configurations, all of which are explicitly contemplated and make part of this disclosure.P_IN1005500

[0072] While the invention has been disclosed with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made, and equivalents may be substituted without departing from the scope of the invention. In addition, many modifications may be made to adapt to a particular situation or material to the teachings of the invention without departing from its scope.

[0073] Throughout the specification and claims, the following terms take the meanings explicitly associated herein unless the context clearly dictates otherwise. The meaning of "a", "an", and "the" include plural references. The meaning of "in" includes "in" and "on." Referring to the FIG.s, like numbers indicate like parts throughout the views. Additionally, a reference to the singular includes a reference to the plural unless otherwise stated or inconsistent with the disclosure herein.

[0074] The present invention relates to isoporous membranes and process for preparation of crystalline isoporous membranes with a well-defined isoporous, active separation layer, particularly nanofiltration membrane with chemical formula 1 Qi4H22[K4P8W4sOi84].12H2O, designed for accurate molecular separation. More specifically, the present invention encompasses the fabrication of an isoporous membrane using intrinsically porous materials having chemical formula 1 Qi4H22[K4PsW48Oi84].12H2O, wherein Q is quaternary ammonium salts (NR4+), wherein R is an alkyl group consisting of C4 -C10 carbon chain. Further, isoporous membrane is coated onto an ultrafiltration support for membrane-based separation in aqueous systems.

[0075] In the embodiment of the present invention provides an isoporous free-standing thin film membrane of functionalized isoporous polyoxometalate with formula 1

[0076] Q14H22[K4P8W48O184].12H2O.

[0077] Formula 1

[0078] Wherein Q is quaternary ammonium salts (NR4+), where R is hydrocarbon containing group selected from the group consisting of [C4 to C10] carbon chain.

[0079] In aspect of the present invention, a thin film composite (TFC) isoporous membrane comprises:P_IN1005500

[0080] a) a thin film of functionalized isoporous polyoxometalates of formula 1 \Qi4 H22 [K4P8W48O184] .I2H2O], wherein Q is quaternary ammonium salts (NR4+), R is an alkyl group consisting of C4 -C10 chain;

[0081] b) an ultrafiltration support.

[0082] In embodiment of the present invention, wherein compound of formula 1 is selected from tridecatetrabutyl ammonium tetra potassium octatetracontatugsto(VI) octaphosphate(V) (Pl QI), tridecatetrahexylammonium tetra potassium octatetracontatugsto(VI) octaphosphate(V) (P1Q2), tridecatetraheptylammonium tetra potassium octatetracontatugsto(VI) octaphosphate(V) (P1Q3), tetradecatetrakis(decyl)ammonium tetra potassium octatetracontatugsto (VI) octaphosphate(V) (P1Q4).

[0083] In another embodiment of the present invention, wherein R is alkyl group selected from the group consisting of tetrabutyl, tetrahexyl, tetraheptyl or tetradecyl.

[0084] In another embodiment of the present invention, wherein quaternary ammonium salts (NR4+) in compound of formula 1 is selected from tetrabutyl ammonium bromide, tridecatetrahexylammonium bromide, tridecatetraheptylammonium bromide and tetradecatetrakis(decyl)ammonium bromide.

[0085] In another embodiment of the present invention, wherein ultrafiltration support selected from poly ether sulphone (PES) or polyacrylonitrile (PAN).

[0086] In another embodiment of the present invention, wherein process for the preparation of thin film membrane of functionalized isoporous polyoxometalates of formula 1 Q14 H22 [K4P8W480184] .I2H2O via cation exchange strategy comprising the steps of:

[0087] a) dissolving dicontaoctapotassium pentalithium octatetracontatugsto(VI) octaphosphate(V) (Pl) in DI water (solution A);

[0088] b) dissolving tetraalkyl ammonium bromide (Q) in polar aprotic or nonpolar solvent or mixture of polar aprotic and nonpolar solvent (solution B);P_IN1005500

[0089] c) adding solution, A in solution B and stirred continuously in the range of 800-1200 rpm at temperature in the range of 25 °C to 30°C for a time period in the range of 4-24 hrs to obtain biphasic solution;

[0090] d) separating the biphasic solution obtained in step (c), followed by evaporation of organic solvent led to the solid or highly viscous material;

[0091] e) dissolving viscous material obtained in step (d) in hexane and dispersing on the deionized (DI) water bowl to form freestanding isoporous film (TFP1Q2);

[0092] f) transferring isoporous film (TFP1Q2) onto the ultrafiltration support to obtain thin film composite (TFC) membrane;

[0093] g) washing the thin film composite (TFC) membrane with water and dried at temperature in the range of 25-30 °C for the time range of 24-30 hours, followed by curing at temperature in the range of 5-10° C in water for time period in the range of 4-5 hours.

[0094] In another embodiment of the present invention, wherein the tetra alkyl ammonium bromide is selected from the group consisting of tetrabutyl ammonium bromide, tetrahexyl ammonium bromide, tetraheptyl ammonium bromide and tetradecyl ammonium bromide.

[0095] Yet another embodiment of the present invention, wherein the polar solvent is selected from water, methanol or acetonitrile.

[0096] Yet another embodiment of the present invention, wherein nonpolar solvent is selected from toluene, xylene, hexane or heptane.

[0097] Yet another embodiment of the present invention, wherein tetraalkyl ammonium bromide in polar aprotic or nonpolar solvent or mixture of polar aprotic and nonpolar solvent in the ratio of 1 : 1 (v / v) wherein the ratio of tetraalkyl ammonium bromide and solvent is in the ratio of 0.002:1:1 (w:v:v)

[0098] The present invention provides the isoporous membranes made up of functionalized porous polyoxometalate thin films of formula 1 for selective separation.P_IN1005500

[0099]

[0100] Q14H22[K4P8W48O184].12H2O

[0101] Formula 1

[0102] Wherein Q is quaternary ammonium salts (NR4+), where R is hydrocarbon containing group selected from the group consisting of [C4 to C10] alkyl.

[0103] The compound of formula 1 is tridecatetrabutyl ammonium tetra potassium octatetracontatugsto(VI) octaphosphate(V) (P1Q1), tridecatetrahexyl ammonium tetra potassium octatetracontatugsto(VI) octaphosphate(V) (P1Q2), tridecatetraheptylammonium tetra potassium octatetracontatugsto(VI) octaphosphate(V) (P1Q3), tetradecatetrakis(decyl)ammonium tetra potassium octatetracontatugsto (VI) octaphosphate(V) (P1Q4).

[0104] In another embodiment of the present invention provides a process for the membrane preparation of functionalized porous polyoxometalate [P1Q1] comprising the steps of:

[0105] a) The reaction mixture of dicontaoctapotassium pentalithium octatetracontatugsto(VI) octaphosphate(V) and tetrabutyl ammonium bromide dissolved in polar solvent selected form water and methanol to followed by stirring the reaction mixture at temperature ranging from 2°C to 30°C for the period ranging from 1 h to 2 h to obtain white colored solid crude of tridecatetrabutylammonium tetra potassium octatetracontatugsto (VI) octaphosphate (V) Completion of reaction, separation of the product and purity of compound was analyzed with the help of spectroscopy , crystallization was done using polar aprotic solvent (For example acetonitrile, acetone, ethyl acetate etc);

[0106] b) Thin film of the tridecatetrabutylammonium tetra potassium octatetracontatugsto(VI) octaphosphate (V) was developed using a combination of polar solvent selected form waterP_IN1005500

[0107] and non-polar solvent selected from toluene and dispersed on water bath at temperature in the range of 25-35°C for period in the range of 4 h to 20 h, allow it to grow on the water surface;

[0108] c) The thin film composite membranes were prepared by transferring the thin films of P 1 Q 1 on ultrafiltration support. Before placing any solutions in the bowl for interfacial film preparation, support was attached to a steel stand through adhesive tape. The steel stand with the support was placed in the bowl, and then bowl was filled with water (250 mL). Followed by the addition of solution of P1Q1 solution in in suitable solvent, to yield free-sanding thin film under controlled evaporation at RT (25-35°C) under 50-60% humidity. Later on, thin films were carefully transferred from the interface on the PES ultrafiltration support attached to the steel stand. The membranes were drained of residual water and dried at room temperature (25 °C), for 24 hours, followed by curing at temperature in the range of 5-10°C in water for the time period in the range of 4 to 5 hours.

[0109] The compound of formula 1 is tridecatetrahexylammonium tetra potassium octatetracontatugsto(VI) octaphosphate(V) (P1Q2) [P1Q2], tridecatetraheptylammonium tetra potassium octatetracontatugsto(VI) octaphosphate(V) (P1Q3) [P1Q3], tetradecatetrakis(decyl)ammonium tetra potassium octatetracontatugsto (VI) octaphosphate(V) (P1Q4) [P1Q4],

[0110] The invention also provides a process for the membrane preparation of functionalized porous polyoxometalate P1Q2, P1Q3 and P1Q4 comprising the steps of:

[0111] a) The reaction mixture of dicontaoctapotassium pentalithium octatetracontatugsto(VI) octaphosphate(V) and tetrahexyl ammonium bromide dissolved in polar (For example water) and non-polar ((For example toluene) solvent followed by stirring the reaction mixture at temperature ranging from 25°C to 30°C for the period ranging from 4 h to 6 h to obtain white colored sticky crude of Tridecatetrahexylammonium tetra potassium octatetracon tatugsto( VI) octaphosphate( V) ;P_IN1005500

[0112] b) Completion of reaction, separation of the product and purity of compound was analyzed with the help of spectroscopy, purification was done using non-polar ((For example hexane) solvent;

[0113] c) Thin film of the tridecatetrahexylammonium tetra potassium octatetracontatugsto(VI) octaphosphate(V) was developed using a non-polar (For example hexane, toluene, xylene) solvent and dispersed on water bath at temperature in range of 25-35°C for the time period in the range of 1 h to 2 h, allow it to grow on the water surface. Similar synthetic approach adapted for P1Q3 and P1Q4, where tetraheptyl ammonium bromide and tetradecyl ammonium bromide used respectively;

[0114] d) TFC membranes were prepared by transferring thin films of PIQn onto ultrafiltration supports. The films were formed via interfacial polymerization at air-water interface under controlled evaporation. The membranes were dried, cured in water, and finalized for testing.

[0115] The permanently porous polyoxometalate (POM) cluster (Pl) with 1 nm integrated pore were functionalised as factionalized porous POM (PIQn (where, Qn= [CnH2n+i]4N+) here, n =4 to 10) to incorporate mechanical properties like flexibility and elasticity, water stability and processability to prepare large area thin films for aqueous separations.

[0116] The porous Pl (K2sLi5H7[PsW48Oi84].92H2O) were functionalised with Qnto yield bulk PlQnby exchanging the K+ / Li+ions of Pl by quaternary ammonium salts (NR4+). The Pl crystals were taken in deionised water and solubilized by adjusting the pH up to 2.0 with addition of 0.5 M H2SO4. This pH-adjusted solution of Pl was added to solution of Qnin a suitable solvent like water, methanol, hexane, toluene, Acetonitrile or xylene; followed by vigorous stirring for 1 h to 24 h, after ion exchanged reaction resulted white precipitates or oily viscus product which was further recrystalize or reproduced in suitable solvent leads to the PlQnyield with formula 1.

[0117] The free-standing thin films of formula 1 were grown at the air-liquid interface. The purified PIQn in required amount (3 mg, 0.35 pmol) was dissolved in solvent selected from Toluene, xylene, hexane, heptane, acetonitrile or mixture of solvent at room temperature 25-35°C and poured over the deionized water in a glass bowl to yield thin films. The free-standing thin filmP_IN1005500

[0118] was extracted within 4 to 12 hrs of slow evaporation at evaporation at RT (25-35°C) under 50-60% humidity based on solvent.

[0119] The composite membranes were prepared by transferring the thin films of PlQnon ultrafiltration support like poly ether sulphone (PES), and polyacrylonitrile (PAN). Before placing any solutions in the bowl for interfacial film preparation, support was attached to a steel stand through adhesive tape. The steel stand with the support was placed in the bowl (72 cm2area), and then bowl was filled with water (250 mL). Followed by the addition of solution of PlQn solution in solvent selected form group consisting of Toluene, xylene, hexane, heptane, acetonitrile or mixture thereof to yield free-sanding thin film under controlled evaporation at RT (25°C) under 50-60% humidity. After that, thin films were carefully transferred from the interface on the PES support attached to the steel stand. The membranes were drained of residual water and dried at room temperature (25 °C), for 24 hours, followed by curing at 5-10° C in water for time period in the range of 4 to 5 hours.

[0120] The separation performance of the thin film composite membranes was tested in a cross-flow filtration setup. Feed solution (~ 1 L) was pumped from a feed tank by using a diaphragm pump into the membrane cell. The effective area of the membranes used in the cell was 16 cm2. Membranes were pre-compacted for at least 4 h under 1 bar pressure by using pure water to reach the steady-state condition. The permeate flux was determined by measuring the weight change with respect to time. Rejection of organic molecules (100 ppm) was also evaluated by measuring the absorbance of the feed and permeate solutions using a UV-Visible instrument. The separation performance of the membranes was analysed using modelled organic molecules having different molecular dimension (nm2). The concentration of molecular markers in the permeate and the feed was measured by UV-visible spectroscopy.

[0121] Examples

[0122] The following examples, which include preferred embodiments, will serve to illustrate the practice of this invention, it being understood that the particulars shown are by way of example and for purpose of illustrative discussion of preferred embodiments of the invention and therefore should not be construed to limit the scope of the present invention.P_IN1005500

[0123] In examples, the quantities and percentages are given by weight unless stated otherwise.

[0124] Example la (I): Synthesis of functionalized porous polyoxometalate P1Q1 and thin film of P1Q1: Tridecatetrabutylammonium tetrapotassium octatetracontatugsto(VI) octaphosphate (v)

[0125] The P1Q1 was synthesized by counter cation exchange strategy, where potassium ions of Pl were displaced by tetrabutylammoniumbromide (Q4Br). The synthesized pure Pl (1.0 g, 0.071 mmol, 1.00 eq.) crystals were dissolved in 40 mL DI water and the Pl containing aqueous solution was added to 20 mL water containing tetrabutylammonium bromide (Q4Br) (4 g, 36.4 mmol, 13.00 eq), resulting in a slurry followed by continuous stirring of the for 4 hours. After filtration of the white precipitate, dried in an air for overnight and recrystallize in 3 times [FIG.

[0126] 11 (a)]. Yield: 0.79

[0127] Thin films of formula 1 containing confined crystalline molecular domains of Pl were grown using bottom-up approach at the air-liquid interface. The purified P1Q1 (3-5 mg) was dissolved in acetonitrile: toluene (1:2) (10-20 ml) at room temperature and poured over the deionized water (280 ml) in a glass bowl to yield thin films of TFP1Q1. The self-supporting TFP1Q1 of nanometer thickness (-30-500) nm were extracted within 1 to 2 hours of slow evaporation at RT (25 °C) under 50% humidity. The large area TFP1Q1 were obtained in an area of -72 cm2 area glass bowl.

[0128] The TFC membranes were prepared by transferring the thin films of P1Q1 on ultrafiltration support like poly ether sulphone (PES). Before placing any solutions in the bowl for interfacial film preparation, support was attached to a steel stand through adhesive tape. The steel stand with the support was placed in the bowl (72 cm2area), and then bowl was filled with water (250 mL). Followed by the addition of solution of P1Q1 in acetonitrile: toluene (1:2), to yield free-sanding thin film under controlled evaporation at RT (25 °C) under 50-60% humidity. Later on, thin films were carefully transferred from the interface on the PES support attached to the steel stand. The membranes were drained of residual water and dried at room temperature (25 °C), for 24 hours, followed by curing at 5° C in water for 4 to 5 hours.P_IN1005500

[0129] Example la (II): Synthesis of functionalized porous polyoxometalate P1Q2 and thin film of P1Q2: Tridecatetrahexylammonium tetrapotassium octatetracontatugsto(VI) octaphosphate (V)

[0130] The P1Q1 was synthesized by counter cation exchange strategy, where potassium ions of Pl were displaced by tetrahexylammoniumbromide (QeBr). The synthesized pure Pl (1.0 g, 0.071 mmol, 1.00 eq.) crystals were dissolved in 40 mL DI water and the Pl containing aqueous solution was added to 50 mL toluene containing tetrahexylammoniumbromide (QeBr) (3.8 g, 2.5 mmol, 13.00 eq), resulting in a suspension followed by continuous stirring of the suspension for 4 hours. Initially, the toluene layer becomes hazy but upon vigorous stirring for 24 h both the layers become clear and organic layer was separated. After removal of the toluene under reduced pressure, the light yellow oily viscous liquid was obtained. Upon vigorous stirring with 50 ml of hexane for 1 h resulted into white precipitate of unreacted counter ion. Upon removal of hexane under reduced pressure yielded pale yellow viscous product [FIG.11 (b)] . Y ield: 0.7 g- The purified P1Q2 (3-5 mg) was dissolved in Hexane (10-20 ml) at room temperature and poured over the deionized water (280 ml) in a glass bowl to yield thin films of TFP1Q2. The self-supporting TFP1Q2 of nanometer thickness (-30-400 nm was extracted within 4 hrs of slow evaporation at RT (25 °C). The large area TFP1Q2 were obtained in an area of -72 cm2.

[0131] The TFC membranes were prepared by transferring the thin films of P1Q2 on ultrafiltration support like polyether sulphone (PES). Before placing any solutions in the bowl for interfacial film preparation, support was attached to a steel stand through adhesive tape. The steel stand with the support was placed in the bowl (72 cm2area), and then bowl was filled with water (250 mL). Followed by the addition of solution of P1Q2 in 10 ml hexane, to yield free-sanding thin film under controlled evaporation at RT (25 °C) under 50-60% humidity. Later on, thin films were carefully transferred from the interface on the PES support attached to the steel stand. The membranes were drained of residual water and dried at room temperature (25 °C), for 24 hours, followed by curing at 5° C in water for 4 to 5 hours.P_IN1005500

[0132] Example la (III): Synthesis of functionalized porous polyoxometalate P1Q3 and thin film of P1Q3: Tridecatetraheptylammonium tetrapotassium octatetracon tatugsto( VI) octaphosphate (v)

[0133] The P1Q3 was synthesized by counter cation exchange strategy, where potassium ions of Pl were displaced by tetraheptylammoniumbromide (Q?Br). The synthesized pure Pl (1.0 g, 0.071 mmol, 1.00 eq.) crystals were dissolved in 40 mL DI water and the Pl containing aqueous solution was added to 50 mL toluene containing tetraheptylammoniumbromide (Q?Br) (4.5 g, 2.5 mmol, 13.00 eq), resulting in a suspension followed by continous stirring of the suspension for 4 hours. Initially, the toluene layer becomes hazy but upon vigorous stirring for 24 h both the layers become clear and organic layer was separated. After removal of the toluene under reduced pressure, the light yellow oily viscous liquid was obtained. Upon vigorous stirring with 50 ml of hexane for 1 h resulted into white precipitate of unreacted counter ion. Prouct was reproduced in hexane 4 to 5 times [FIG. 11 (c)]. Yield: 0.65 g.

[0134] The purified P1Q3 (3-5 mg) was dissolved in Hexane (10-20 ml) at room temperature and poured over the deionized water (280 ml) in a glass bowl to yield thin films of TFP1Q3. The self-supporting TFP1Q3 of nanometer thickness (-50-300 nm) were extracted within 4 hrs of slow evaporation at RT (25 °C) under 50% humidity. The large area TFP1Q3 were obtained in an area of -72.

[0135] The TFC membranes were prepared by transferring the thin films of P1Q3 on poly ether sulphone (PES). Before placing any solutions in the bowl for interfacial film preparation, support was attached to a steel stand through adhesive tape. The steel stand with the support was placed in the bowl (72 cm2area), and then bowl was filled with water (250 mL). Followed by the addition of solution of Pl Q3 in 10 ml hexane, to yield free-sanding thin film under controlled evaporation at RT (25 °C) under 50-60% humidity. Later on, thin films were carefully transferred from the interface on the PES support attached to the steel stand. The membranes were drained of residual water and dried at room temperature (25 °C), for 24 hours, followed by curing at 5° C in water for 4 to 5 hours.P_IN1005500

[0136] Example la (IV): Synthesis of functionalized porous polyoxometalate P1Q2 and thin film of P1Q2: Tridecatetrakis(decyl)ammonium tetrapotassium octatetracontatugsto(VI) octaphosphate (v)

[0137] The P1Q4 was synthesized by counter cation exchange strategy, where potassium ions of Pl were displaced by tetrakis(decyl)ammoniumbromide (QioBr). The synthesized pure Pl (1.0 g, 0.071 mmol, 1.00 eq.) crystals were dissolved in 40 mL DI water and the Pl containing aqueous solution was added to 50 mL toluene containing tetrakis(decyl)ammoniumbromide (QioBr) (6.7g, 2.5 mmol, 13.00 eq), resulting in a suspension followed by continuous stirring of the suspension for 4 hours. Initially, the toluene layer becomes hazy but upon vigorous stirring for 24 h both the layers become clear and organic layer was separated. After removal of the toluene under reduced pressure, the light yellow oily viscous liquid was obtained. Upon vigorous stirring with 50 ml of hexane for 1 h resulted into white precipitate of unreacted counter ion. The product was reproduced 4 to 5 times in hexane [FIG. 11 (d)]. Yield: 1.3 g.

[0138] The purified P1Q4 (3-5 mg) was dissolved in Hexane (10-20 ml) at room temperature and poured over the deionized water (280 ml) in a glass bowl to yield thin films of TFP1Q4. The self-supporting TFP1Q4 of nanometer thickness (-50-400 nm) were extracted within 1-2 hrs of slow evaporation at RT (25 °C) under 50% humidity. The large area TFP1Q4 were obtained in an area of -72 cm2.

[0139] The TFC membranes were prepared by transferring the thin films of P1Q4 on poly ether sulphone (PES). Before placing any solutions in the bowl for interfacial film preparation, support was attached to a steel stand through adhesive tape. The steel stand with the support was placed in the bowl (72 cm2area), and then bowl was filled with water (250 mL). Followed by the addition of solution of P1Q4 in 10 ml hexane, to yield free-sanding thin film under controlled evaporation at RT (25 °C) under 50-60% humidity. Later on, thin films were carefully transferred from the interface on the PES support attached to the steel stand. The membranes were drained of residual water and dried at room temperature (25 °C), for 24 hours, followed by curing at 5° C in water for 4 to 5 hours.P_IN1005500

[0140] Example 2: Separation performance of functionalized porous polyoxometalate thin film from P1Q1-P1Q4

[0141] The separation performance of the thin film composite membrane of functionalized porous polyoxometalate, P1Q1 to P1Q4 were tested in a cross-flow filtration setup [Table-1]. Feed solution (~ 1 L) was pumped from a feed tank by using a diaphragm pump into the membrane cell. The effective area of the membranes used in the cell was 16 cm2. Membranes were precompacted for at least 4 h under 1 bar pressure by using pure water to reach the steady-state condition. Membrane permeances was calculated using the following equation (1):

[0142] P = V / A.t p

[0143] where V is the volume of the permeate in litres, t (h) is the collection time, A (m2) is the effective area of the membrane used, Ap (bar) is the transmembrane pressure.

[0144] Membrane permeances were continuously monitored and the feed and permeate solutions were collected for the analysis. The separation performance of the membranes was analysed using different molecular markers added in the feed solution. The concentration of 7-hydroxy-2-naphthalenesulfonic (SNF), methyl orange (MO), acid orange (AO), orange G (OG), acid fuchsin (AF), congo red (CR), brilliant blue R (BBR), p-nitro aniline (PNA), methyl red (MR), calcian reagent (CaR), methylene blue (MB), safranine O (SO), Janus Green B (JGB) and Alcian Blue (AB) in the feed was 0.1 g.L-1. The concentration of dyes in the permeate and the feed was measured by the UV-visible absorbance or gel permeation chromatography based on molecular markers. The rejection (R) of membranes was calculated as a percentage according to the following equation (2):

[0145] (%) = (1 -CpICf) x 100

[0146] Where, Cp(in g.L1) and Cf (in g.L1) are the concentrations of solutes in the permeate and the

[0147] feed, respectively. At least four membrane coupons were tested to get an average value and

[0148] standard deviation.P_IN1005500

[0149] Aii Nl Ciittnonceuraaonc

[0150] Table- 1: Separation performance of membrane of functionalized porous polyoxometalate (P1Q1-P1Q4)

[0151] Charge No. Molecular Molecular Area molecular markers

[0152] of markers weight (nm2) Q1P1 Q2P1 Q4P1 Q3P1 molecule

[0153] Permeance Rejection Permeance Rejection Permeance Rejection Permeance Rejection (Ltn2h (%) (Lm2h (%) (Lm -h (%) (Lm2k (%) ’bar1) ’bar1) ’bar1) ’bar1}

[0154] ± ± ± ± ± ± 1. Pure 26.35 4 20.36 4 8.4 5 76 5 water

[0155] 2 SNF 246.21 043 24.26 X 32.2 20 3 44.4 4 841 3 42.2 7 73 4 24 4 3. MO 327.33 0.75 24.41 41.1 4 20.2 3 50.4 3 9 7 51.7 6 70 4 26 4. AO 350.32 0.86 22.84 3 43.9 4 21.15 2 54.1 3 9 17 2 47.6 4 67 3 3? 4 PTS 61043 1 243 2 98.7 20.85 3 99.6 845 3 99.4 65 4 98 6. OG 452.38 1.1 22.7 5 94.5 2 7 2 94.8 4 9 34 2 96.1 2 63 4 75 3 7. AF 585 54 1.18 248 2 94.1 2 21.82 3 96.2 7 9 55 3 98.5 1 59 3 76 4 8. CR 696.67 1.98 17 3 99.3 17 T* 99.8 684 7 99.8 54 4 98 9. BBR 825 97 2.94 16 3 99.4 16.14 7 99.9 6 13 99.9 50 4 99

[0156] 10. PNA 138 12 0.33 24 87 ? 12.2 3 2045 3 15.4 3 849 3 19.3 4 73 3 13.2 3 11. MR 269.3 0.81 22.83 3 22.6 4 21.12 7 46.2 3 900 7 50.3 7 71 2 14.7 4 12. CaR 622.54 1.37 21.32 76.4 3 21.85 2 92.4 7 907 91.9 3 69 7 48.4 3

[0157] 13. MB 319.85 0.64 24.77 3 7.6 7 19.86 2 13.4 3 8.2 3 12.3 6 74 4 7.6 7 14. SO 350,85 0.86 25.18 3 14.1 19.35 •> 25.1 4 872 3 43.2 4 75 3 9.4 A 15. JGB 511.06 1.56 21.32 z, 98.1 1 16.12 99.5 5 69 7 99.4 69 ? 94.2 7

[0158]

[0159] 16, A1 B 1298.86 7 s 2089 3 99.4 15.69 3 99.6 5 12 7 99.8 67 3 99.1

[0160] ADVANTAGES OF THE INVENTION

[0161] 1. Well-defined Iso-porous Membranes: Developed membranes with precise, crystalline iso-pores, addressing a major challenge in molecular separation.

[0162] 2. Crystalline Polyoxometalate Films: present invention offers defect-free, highly crystalline polyoxometalate (POM) films, providing a new source for molecular separation.

[0163] 3. Mechanical Robustness: Crystalline polyoxometalate (POM) films are mechanically strong, overcoming the challenge of assembling pores into a defect-free, robust structure.

[0164] 4. Tunable Thickness & Large Size: crystalline polyoxometalate (POM) films feature adjustable thickness (>30 nm) and large lateral size (50 cm2), offering scalability and versatility.P_IN1005500

[0165] 5. Innovative Self-Assembly: Short-chain molecular entanglement approach has been used to self-assemble 1 nm pores of POMs, ensuring defect-free continuous thin films.

[0166] 6. Superior Separation Efficiency: The well-arranged pores improve separation efficiency, effectively targeting molecules larger than 1 nm2(Stokes radii), with reduced pore size distribution.

Claims

P_IN1005500We Claim:

1. An isoporous free-standing thin film composite (TFC) isoporous membrane comprises: a) a thin film of functionalized isoporous polyoxometalates of formula 1 \Qi4 H22 [K4P8W480184] .I2H2O], wherein Q is quaternary ammonium salts (NRV); R is an alkyl group consisting of C4 -C10 carbon chain;b) an ultrafiltration support.

2. The isoporous free-standing thin film composite (TFC) isoporous membrane as claimed in claim 1 , wherein compound of formula 1 is selected from tridecatetrabutyl ammonium tetra potassium octatetracontatugsto(VI) octaphosphate(V) (P1Q1), tridecatetrahexylammonium tetra potassium octatetracontatugsto(VI) octaphosphate(V) (P1Q2), tridecatetraheptylammonium tetra potassium octatetracontatugsto(VI) octaphosphate(V) (P1Q3), tetradecatetrakis(decyl)ammonium tetra potassium octatetracontatugsto (VI) octaphosphate(V) (P1Q4).

3. The isoporous free-standing thin film composite (TFC) isoporous membrane as claimed in claim 1 , wherein quaternary ammonium salts (NRV) in compound of formula 1 is selected from tetrabutyl ammonium bromide, tridecatetrahexylammonium bromide, tridecatetraheptylammonium bromide and tetradecatetrakis(decyl)ammonium bromide.

4. The isoporous free-standing thin film composite (TFC) isoporous membrane as claimed in claim 1, wherein ultrafiltration support is selected from poly ether sulphone (PES) or polyacrylonitrile (PAN).

5. A process for the preparation of thin film membrane of functionalized isoporous polyoxometalates of formula 1 Q14 H22 [K4P8W48O184] .I2H2O as claimed in claim 1, wherein cation exchange strategy process comprising the steps of:a) dissolving dicontaoctapotassium pentalithium octatetracontatugsto (VI) octaphosphate(V) (Pl) in deionized (DI) water to form a solution A;b) dissolving tetraalkyl ammonium bromide (Q) in polar aprotic or nonpolar solvent or mixture of polar aprotic and nonpolar solvent to form a solution B;c) adding the solution A in the solution B and stirred continuously in the range of 800- 1200 rpm at temperature in the range of 25°C to 30 °C for a time period in the range of 4-24 hours to obtain a biphasic solution;P_IN1005500d) separating the biphasic solution obtained in step (c), followed by evaporation of organic solvent led to a solid or highly viscous material;e) dissolving the viscous material obtained in step (d) in hexane and dispersing on the deionized (DI) water bowl to form a freestanding isoporous film (TFP1Q2);f) transferring the isoporous film (TFP1Q2) onto the ultrafiltration support to obtain a thin film composite (TFC) membrane;g) washing the thin film composite (TFC) membrane with water and dried at temperature in the range of 25-30°C for the time period in the range of 24-30 hours, followed by curing at temperature in the range of 5-10° C in water for time period in the range of 4- 5 hours.

6. The process for the preparation of thin film membrane as claimed in claim 5, wherein the tetra alkyl ammonium bromide is selected from the group consisting of tetrabutyl ammonium bromide, tetrahexyl ammonium bromide, tetraheptyl ammonium bromide and tetradecyl ammonium bromide.

7. The process for the preparation of thin film membrane as claimed in claim 5, wherein the polar aprotic solvent is selected from the group consisting of water, methanol, acetonitrile and mixture thereof and the nonpolar solvent is selected from the group consisting of toluene, xylene, hexane or heptane.

8. The process for the preparation of thin film membrane as claimed in claim 5, wherein the tetraalkyl ammonium bromide in the polar aprotic or the nonpolar solvent or mixture of the polar aprotic and the nonpolar solvent in the ratio of 1:1 (v / v) wherein the ratio of the tetraalkyl ammonium bromide and the solvent is in the ratio of 0.002: 1: 1 (w:v:v).

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