A 2D Soft Covalent Organic Framework Membrane Prepared via a Molecular Bridge

Abstract

Highly flexible and robust self-standing covalent organic framework (COF) membranes with rapid preparation are important but technically challenging for achieving precise separation. Herein , a novel imine-based 2D soft covalent organic framework (SCOF) membrane with a large area of 226.9 cm² , via ingeniously selecting an aldehyde flexible linker and a trigonal building block, is reported. The soft 2D covalent organic framework membrane is rapidly formed (≈5 min) based on the sodium dodecyl sulfate (SDS) molecular channel constructed at the water/dichloromethane (DCM) interface, which is the record-fast SCOF membrane formation and 72 times faster than that in the reported literature. MD simulation and DFT calculation elucidate that the dynamic, self-assembled SDS molecular channel facilitates faster and more homogeneous transfer of amine monomers in the bulk, thereby forming a soft 2D self-standing COF membrane with more uniform pores. The formed SCOF membrane exhibits superb sieving capability for small molecules, robustness in strong alkaline (5 mol L^-1 NaOH), acid (0.1 mol L^-1 HCl), and various organic solutions, and sufficient flexibility with a large curvature of 2000 m^-1 for membrane-based separation science and technology.

Keywords: 2D soft covalent organic frameworks (SCOFs); SDS molecular bridge; molecular sieving; regulation of reaction kinetics; self-standing membranes.