Catalytic Space Engineering in Porphyrin Metal-Organic Frameworks for Combinatorial CO2 Capture and Conversion under Low Concentration.

Porous porphyrin metal-organic frameworks (PMOFs) provide promising platforms for studying CO2 capture and conversion (C3) owing to their versatility in photoelectric, catalytic, and redox activities and porphyrin coordination chemistry. Herein, we report the C3 application of two PMOFs by engineering the coordination space through the introduction of two catalytic metalloporphyrins doped with rhodium or iridium, Rh-PMOF-1 and Ir-PMOF-1, both of which can serve as heterogeneous catalysts for the chemical fixation of CO2 into cyclic carbonates with yields of up to 99%. Remarkably, the catalytic reactions can effectively proceed under low CO2 concentrations and high yields of 83% and 73% can be obtained under 5% CO2 in the presence of Rh-PMOF-1 and Ir-PMOF-1, respectively. The synergistic effect of the metalloporphyrin ligand and the Zr6O8 cluster, in combination with the CO2 concentration effect from the pore space, might account for the excellent catalytic performance of Rh-PMOF-1 under low CO2 concentration. Recycling tests of Rh-PMOF-1 show negligible loss of catalytic activity after 10 runs.