(644a) Thin-Film Covalent Organic Framework Membranes Made By Interfacial Synthesis for Organic Solvent Nanofiltration

Organic solvent nanofiltration (OSN) relies on the development of robust membranes that are capable of separating organic liquid mixtures and scalable for industrial application. Covalent organic frameworks (COFs) are a new class of porous materials that possess ordered two-dimensional (2D) or three-dimensional (3D) structures, tunable pore size and functionality, and excellent chemical stability, making them promising materials for OSN membranes. Herein, we report the synthesis of β-ketoenamine linked 2D COF and imine-linked 3D COF membranes via a scalable, on-surface interfacial synthesis approach. Continuous thin-film COF membranes with controllable thickness can be directly formed on a variety of supports (ceramic or polymeric) in a matter of minutes or even seconds. Although the resultant membranes possess amorphous structure, they have demonstrated interesting OSN performances, including solvent permeances above 50 L/(m2.h.bar), molecular weight cutoff in the range of 500-1000 g/mol, and good solvent stability. The diffusion and reaction kinetics of the monomers were found to be important factors influencing the membrane structures. Detailed membrane structure characteristics, their correlations with key synthetic parameters, solvent transport and solute rejection mechanisms of these 2D and 3D COF membranes will also be discussed.