Indium-captured zirconium-porphyrin frameworks displaying rare multi-selectivity for catalytic transfer hydrogenation of aldehydes and ketones

Abstract

Selective catalytic transfer hydrogenation (CTH) of carbonyl compounds to obtain specific alcohols holds significant importance across various fields. Achieving multiple selectivity in CTH is particularly crucial, but full of great challenge. Herein, a cationic In-captured Zr-porphyrin framework (1) with nanosized pores/cages was successfully constructed and showed high structure stability. Catalytic investigations revealed that 1 displayed highly multi-selective CTH of aldehydes and ketones containing both chemo- and size selectivity for the first time. The CTH of aldehydes and ketones exhibited remarkable reductive selectivity of 99% towards CO bonds into CHOH in the presence of -NO₂, -CN and CC groups. Through tuning the reaction conditions, 1 also exhibited highly selective reduction of 97% for -CHO groups in the simultaneous presence of -CHO and -COCH₃ groups in intra- and intermolecular settings. Remarkably, reductive selectivity towards -CHO group remained prominent among five concurrent unsaturated groups mentioned above. Additionally, the definite pore size of 1 facilitated volume control of substrates, enabling size selectivity. 1 as a heterogeneous catalyst was further confirmed by leaching tests, and maintained high activity even after being used for at least six cycles. Mechanistic studies have revealed that Zr₆O₈ clusters served as the catalytic centers and the observed chemoselectivity mainly results from the synergistic effect of distinct metal sites within 1. The heightened selectivity towards -CHO over -COCH₃ can be attributed to the easier realization of transfer hydrogenation processes for -CHO compared to -COCH₃.