2D titanium catecholate metal-organic frameworks with tunable gas adsorption and ionic conductivity

2D titanium(iv)-based metal-organic frameworks (2D Ti-MOFs) have attracted great interest in recent years due to the high abundance and hypotoxicity of Ti. The construction of Ti-MOFs with a single node TiO₆ cluster not only offers a high utilization of Ti atoms but also provides dedicated physicochemical properties. Among TiO₆ cluster-based Ti-MOFs, 2D titanium catecholate MOFs are rare and less explored. Herein, we constructed a series of 2D Ti-catecholate MOFs (Ti-DMTHA-M, where M = Li, Na, K) composed of a triangular Ti(C₂O₂)₃ single metal secondary building unit (SBU) and the anthracene ligand, 9,10-dimethyl-2,3,6,7-tetrahydroxyanthracene (DMTHA). The extended 2D anionic framework of Ti-DMTHA-M was formed by reticulating Ti(C₂O₂)₃ and DMTHA in a hcb topology. The counter cations in the pores of Ti-DMTHA-M greatly influence gas adsorption and solid-state ion conduction. The ion conductivity of Ti-DMTHA-M shows a gradually increasing trend when the counter ion is shifted from Li to K, which was investigated both experimentally and theoretically.