Synergistic effect of organic metal chalcogenides acid-base pairs for enhancing proton conduction

[Display omitted] •A novel proton conductive composite membrane was successfully constructed by two 2D OMCs nanosheets covered by long-range ordered surface functional groups.•The long-range ordered acid-base pairs were constructed via the interfacial electrostatic interactions between amino and carboxyl groups from on the surface of OMCs nanosheets.•The efficient proton conduction paths of acid-base pairs significantly promoted the proton conductivity of the composite membrane under low humidity. Acid-base pairs synergistic strategy is one of the most effective ways to improve the proton conductivity of materials at low humidity. However, the random distribution of acid or base functional groups on the surface of the materials are difficult to form long-range ordered proton transfer channels, which hinders the proton conductivity. Herein, two organic metal chalcogenides (OMCs), Ag(SPh-NH2) and Ag(SPh-COOH) nanosheets were self-assembled into composite membranes by vacuum filtration. Benefiting from the long-range ordered acid-base functional groups on the surface of OMCs, the proton conductivity was significantly enhanced. As a result, the proton conductivity of the Ag(SPh-NH2)/Ag(SPh-COOH) composite membrane is greatly improved at a low humidity condition of 45% RH, reaching the level of the single membrane at high humidity. In addition, the proton conductivity of Ag(SPh-NH2)/Ag(SPh-COOH) composite membrane is 47 times higher than that of Ag(SPh-NH2) membrane and 10 times higher than that of Ag(SPh-COOH) membrane under high-temperature hydration state. Collectively, this study broadens the avenue for designing proton-conducting materials that can work under low humidity conditions.