Two Stable Sodalite-Cage-Based MOFs for Highly Gas Selective Capture and Conversion in Cycloaddition Reaction

Stable metal-organic frameworks, containing periodically arranged nanosized cages or pores and active Lewis acid-base sites, are considered ideal candidates for efficient heterogeneous catalysis. Herein, based on the light of reticular chemistry design principles, the ingenious assembly of two pyridine N-rich multifunctional triangular linkers, H3TBA [3,5-di (1h-tetrazol-5-yl) benzoic acid] and H2TZI [5-(1H-tetrazol-5-yl)isophthalic acid], with MnII formed PCP-33(Mn) and PCP-34(Mn), respectively. PCP-33(Mn) and PCP-34(Mn) are typical sod topology zeolitic metal-organic frameworks (ZMOFs) with hierarchical tetragonal micropores and metal organic polyhedral sodalite-like cages. The inner walls of these cages are modified by open metal sites MnII and Lewis acid-base sites of halide ions and N pyridine atoms. The characteristics of the cages' structures make two MOFs exhibit high surface area and a small window, which promote their outstanding gas capture ability (C2H2, 131.8 cm3 g-1; CO2, 77.9 cm3 g-1 at 273 K) and selective separation performance (C2H2/CH4, 226.2, CO2/CH4, 50.3 at 298 K), and are also suitable as catalytic reactors for metal/solvent-free chemical fixation of CO2 with epoxides to achieve high-efficiency CO2 conversion. Furthermore, they are greatly recyclable for several cycles while retaining their structural rigidity and catalytic activity.