Hydrogel-Woven COF Membranes With Orthogonal, Opposite Thermoresponsive Nanochannels: Overcoming the Permeance-Selectivity Trade-off.

Abstract

Smart membranes, characterized by unique stimuli-responsive channels to dynamically alter their chemistry and structure for orchestrating mass transport, are highly promising to gain extraordinary sieving performance over conventional membranes. However, smart membranes are locked by formidable trade-off between permeance and selectivity during stimuli-responsive process, owing to their synchronous, homogeneous stimuli-responsive changes in channels. Here, we discover a new kind of smart membranes, hydrogel-woven covalent organic framework (HW-COF) membranes with orthogonal, opposite thermoresponsive nanochannels, overcoming the permeance-selectivity trade-off for achieving extraordinary aqueous separation. The key of HW-COF membranes lies in the photothermal-driven in-situ confined weaving of poly(N-isopropylacrylamide) hydrogel networks within orthogonal in-plane pores and interlayer channels of two-dimensional COF membranes for yielding mechanical interlocking architecture. Distinct from the non-interlocked counterpart, HW-COF membranes showcase a positive response in in-plane pores yet a negative response in interlayer channels. This unique thermoresponsive behavior can be tailored by the synergy of in-plane pores and interlayer channels, allowing HW-COF membranes to obtain markedly positive response in both permeance and selectivity, almost not achievable with reported smart membranes. As a concept of demonstration, HW-COF membranes can be applied for sieving water isotopologue with ultrahigh selectivity (90.9%) and permeance (16.6 L m^-2 h^-1bar^-1) using low-grade heat as stimuli.