A multifunctional anionic metal-organic framework for high proton conductivity and photoreduction of CO2 induced by cation exchange.

Metal-organic frameworks (MOFs) provide an ideal platform for loading various guests owing to their available space, and can be developed as a class of multifunctional materials. Herein, we cover the design and synthesis of two kinds of exchanged frameworks with multifunctional applications based on H3ImDC and In(NO3)3·2H2O through guest exchange inside the framework. The guest ammonium ion (NH4+) and [Ru(2,2'-bipyridine)3]2+ (Rubpy) are selected to exchange the dimethylammonium cation (Me2NH2+) encapsulated within In-MOF, giving birth to two kinds of new MOFs, named NH4+@In-MOF and Rubpy@In-MOF respectively. The proton conduction of NH4+@In-MOF and the CO2 photoreduction of Rubpy@In-MOF are investigated. Under different test conditions, the proton conductive behaviors of NH4+@In-MOF are evaluated and the best proton conductive value can reach up to 9.81 × 10-3 S cm-1. Compared to the original In-MOF, Rubpy@In-MOF exhibits a significantly enhanced CO2 photoreduction performance under a pure CO2 atmosphere. Furthermore, its photocatalytic activity is retained even under a 10% CO2 gas atmosphere, displaying a synergistic effect between Rubpy and In-MOF24 within Rubpy@In-MOF.