Encapsulation of Single Iron Sites in a Metal–Porphyrin Framework for High-Performance Photocatalytic CO 2 Reduction

Efficient CO 2 reduction with earth-abundant photocatalysts is a highly attractive but very challenging process for chemists. Herein, we synthesized an indium–porphyrin framework, In(H 2 TCPP) (1- n ) [Fe(TCPP)(H 2 O)] (1- n ) [DEA] (1- n ) (In–Fe n TCPP-MOF; H 2 TCPP = tetrakis(4-benzoic acid)porphyrine; DEA = diethylamine), with a porphyrin ring supporting the single-site iron for the high-performance visible-light-driven conversion of CO 2 to CO. A high CO yield of 3469 μmol g –1 can be achieved by a 24 h photocatalytic reaction with a high CO selectivity (ca. 99.5%). This activity was much higher than that of its cobalt analogues or the Fe-free indium-based metal–organic framework (MOF). Systematic experimental and theoretical studies indicate that the porphyrin-supported iron centers in the MOF matrix serve as efficient active sites, which can accept electrons from the photoexcited MOFs in order to mediate CO 2 reduction.