Electrochemical Polymerized Conjugated Microporous Polymer (CMP) Membranes For Ultra-fast Organic Solvent Nanofiltration

Nanofiltration（NF）is an emerging field of membranes separation technology and its separation accuracy is between reverse Osmosis（RO）and ultrafiltration（UF）.Under relative low operating pressure,it can precisely separate polyvalent ions and small molecules with molecular weight less than 1000.At present,NF separation technology includes aqueous solution system and organic solvent system.In the field of chemical,food and pharmaceutical industries,a large number of separation process is carried out in the organic solvent system,therefore NF separation technology in the organic solvent system is important.The material of NF separation membranes is mainly organic polymer material.And the polymer membranes materials are not stable in the organic solvent system.This instability greatly limits the application of NF in organic solvent system.Therefore,how to prepare a NF membranes with high efficiency and good stability has become an crucial issue.Electrochemical polymerization is a method of preparing a polymer membranes using an oxidative or reductive coupling reaction of a precursor molecule at the electrode/solution interface.For the preparation of membranes,the thickness of membranes can be controlled precisely by the electrochemical polymerization technique.And the mass transfer resistance of membranes can be reduced effectively.Thus,a membranes with high separation efficiency was obtained.In addition,Poly-thiophene as a membranes material,because of its own rigid molecular skeleton,rich pore structure and excellent solvent resistance,it can improve the membranes mass transfer efficiency.In this paper,the conjugated microporous polymer membranes（TTB-CMPs）were prepared by electrochemical polymerization using 1,3,5-tri（2-thienyl）-benzene（TTB）as precursors,and the influence of electro-polymerization parameters to the NF separation property of organic solvents had been researched.1.By using cyclic voltammetry method,the TTB-CMPs membranes with different thickness were prepared under the conditions of low monomer concentration,low potential,different scanning cycles and scanning speed.The obtained thinnest TTB-CMPs membranes was selected to test the NF permeation flux and rejection.The results showed that it has high separation efficiency towardorganic solvents.For example,the methanol flux is up to 31.95 L·h^-1·m^-2·bar^-1.Then the small molecules with different molecular weight were selected to test therejection performance of the membranes.The results showed that the membraneshas good rejection to the small molecule with molecular weight of more than 800,and the retention could reach 91.26%.2.In order to further improve the rejection of TTB-CMPs membranes for dye molecules,the pore size of TTB-CMPs membranes was adjusted by oxidation modification.After oxidation,the TTB-CMPs membranes showed much higher rejection to protoporphyrin and bright blue.The rejection of protoporphyrin was increased from the original 72.10%to 96.53%,and the rejection of bright blue increased from the original 91.26%to 96.40%.In this paper,ultra-thin conjugated microporous polymer membranes were prepared by electrochemical polymerization,and the pore size of membranes was adjusted by modification.The conjugated microporous polymer membranes with high flux and rejection were obtained.,This work suggest that TTB-CMPs membranes have an enormous potential in the chemical,food and pharmaceutical industry application.