(642g) Conjugated Polymers for Molecular Separation

The separation performance and permeance of membranes are dependent on pore size uniformity and porosity. To that end, the uniform pore size and porosity of conjugated microporous polymers (CMPs) attracted significant attention from scientific community. With recyclability and sustainability as a societal need for scientific advancement, development of selective nanofiltration membranes is now highly desirable. Along these lines, CMPs, with exceptional resistance to common solvents, are well-posed to be separation materials for solvent filtration. However, the preparation of robust nanofiltration membranes with CMPs is limited due to their brittle nature and their solvent intractability. Herein, we report the development of porphyrin-based CMP filtration membranes from the electropolymerization of 5,10,15,20-Tetrakis(4-aminophenyl)porphyrin (TAPP). To evaluate CMPs performance TAPP was electropolymerized on conductive glass, etched off using potassium hydroxide and then transferred to ultrafiltration supports. The separation performance of TAPP membranes was evaluated for a wide range of dye molecules with the molecular weight ranging from 200 to 1000 Da and in various solvents including water, acetonitrile, ethanol, and methanol. The composite membrane showed a molecular weight cut-off (MWCO) ~ 300 Da with acetonitrile permeance of 1.5 L/m² h bar. To improve the applicability of our membranes, next we fabricated a conductive support layer by filtration of titanium carbide based, MXene, on a nylon support. The as-fabricated MXene-coated membranes were used as conductive substrates for the electropolymerization of TAPP. The composite nanofiltration membranes demonstrated improved mechanical strength, uniform pore size and ductility. The engineered MXene/CMPs nanocomposite membrane exhibited enhanced acetonitrile permeance of 2.2 L/m² h bar without compromise in the solute rejection and MWCO of ~350 Da. We attribute the improved performance of the composite membrane to the as-formed MXene interlayer.