Metal–organic frameworks (MOFs) of an MIL-101-supported iridium(iii) complex as efficient photocatalysts in the three-component alkoxycyanomethylation of alkenes

Abstract

Metal–organic frameworks (MOFs) exhibit intriguing physicochemical properties due to their manageable structure, abundant porosity, and uniform pore size, which provide ideal environments for photocatalysts to achieve highly efficient photocatalysis. In this work, fac-Ir(ppy)₃ is directly anchored to MOFs of MIL-101 with different morphologies via Friedel–Crafts alkylation, affording various MIL-101-supported fac-Ir(ppy)₃ without the molecular modification of fac-Ir(ppy)₃. The as-fabricated photocatalysts possess high specific surface areas (785–962 m² g⁻¹), pore volumes (0.42–0.47 cc g⁻¹) and uniform pore sizes (∼1.9 nm). The luminescence properties of anchored fac-Ir(ppy)₃ including emission lifetime, band gap energy and quantum yield are enhanced by fabricating a hollow interior and double shell in the frameworks of MIL-101 through etching with acetic acid. In the visible light-induced three-component alkoxycyanomethylation of styrenes with bromoacetonitriles and methanol, comparable catalytic activities (66–90%) to homogeneous fac-Ir(ppy)₃ (69–90%) are achieved at room temperature. Furthermore, owing to the good chemical and mechanical stability of the catalyst, no significant decrease in yield (<2%) is observed over ten catalytic cycles. Overall, this study provides a mass/charge transfer-enhanced platform for supported photocatalysts to achieve highly efficient synthesis of fine chemicals in the field of heterogeneous photocatalysis.