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Cobalt–salen-based porous ionic polymers, which are composed of cobalt and halogen anions decorated on the framework, effectively catalyze the CO2cycloaddition reaction of epoxides to cyclic carbonates under ambient conditions. The cooperative effect of bifunctional active sites of cobalt as the Lewis acidic site and the halogen anion as the nucleophile responds to the high catalytic performance. Moreover, density functional theory results indicate that the cobalt valence state and the corresponding coordination group influence the rate-determining step of the CO2cycloaddition reaction and the nucleophilicity of halogen anions.

Covalent bonding is widely adopted in graphene oxide (GO) membrane to improve structural integrity and restrict swelling, while it comes with a price of enlarged d-spacing and sacrifices membrane selectivity. This work offers a facile strategy to break the trade-off between membrane stability and selectivity. Specifically, graphene oxide (GO)/reduced graphene oxide (rGO) hybrid membranes were fabricated by a controlled pre-cross-linking method. With this method, restricted swelling by cross-linking and reduced d-spacing by GO reduction can be achieved simultaneously by controlling reaction time. Membranes were prepared on porous alumina support by vacuum filtration method. Two different d-spacing values (∼12.0 and ∼7.5 Å) were found in the hybrid membrane, representing the layer structures of expanded GO interspacing with inserted cross-linker and reduced layer spacing after GO reduction. The presence of such mixed layer structures enables restricted swelling, excellent mechanical strength, and unique separation property. The hybrid membrane shows excellent permselective H2/CO2separation with a separation factor of 22.93 ± 1.57 and H2permeance of 2.46 ± 0.01× 10–8mol m–2s–1Pa–1. In desalination test with 3.5 wt % sea salt solution, the hybrid membrane shows high ion (Na+, K+, Mg2+, Cl–, and SO42–) rejection rate of above 99%, as well as excellent durability.