▎ 摘　　要

Inspired by biological membranes with charge-gated channels that allow the transport of water and ions but restrict the undesired substances, various regulated nanofiltration (NF) membranes containing charge-gated channels have been developed for water purification. However, most of these membranes are mono-charged (positively or negatively) that show high rejection only to the corresponding co-ions but low rejection to the counter-ions, which limits their wider applications. Herein, we report NF membranes with gas-tunable charge-gated channels and high rejection to different salts on demand. The membranes are prepared by assembling a CO2-responsive polymer, poly(N, N-dimethylaminoethyl methacrylate), on the surface of graphene oxide (GO). As a result of CO2-induced reversal of the charge sign, the membranes exhibit "self-regulation" of their surface charges. Upon bubbling CO2 into water, the membranes are positively charged, which shows high rejection to MgCl2. After bubbling Ar to remove CO2, the membranes gradually transform to negatively charged, and high rejection to Na2SO4 is obtained. This study demonstrates the gas-tunable charge-gated ion transport behavior of the CO2-responsive NF membranes, and opens up new avenues for the design of on-demand NF membranes.