Dual-linker Ir–Zr-MOF shows improved porosity to enhance aqueous sulfide photooxidation

Abstract

The hetero photooxidation of sulfide under aqueous conditions is of great importance in the green synthesis of sulfoxide. This process requires a type of solid photocatalyst with the properties of high porosity and water stability, as well as photosensitivity. Herein, a stable Ir–Zr-MOF material (compound 1) with high porosity is assembled from two linear linkers of a 2-phenylquinoline-4-carboxylic acid-Ir(III) complex (Irphen) and 4,4′-stilbenedicarboxylic acid (H₂SDC), and a Zr₆ cluster. 1 is isostructural to JLU-Liu34 with a composition of [Zr₆O_4.78(OH)_3.22(SDC)_3.82(Irphen)_0.78TFA_2.8]·2.8MeOH and permanent porosity with a BET surface area of 1507 m² g⁻¹. 1 exhibits improved activity for the photocatalytic aerobic oxidation of sulfide to sulfoxide via blue light irradiation under aqueous conditions. Mechanism studies demonstrate that a superoxide radical is the reactive oxygen species in the sulfide photooxidation. 1 can be readily recycled and reused at least 5 times without loss of catalytic activity. This work not only provides a good strategy for the assembly of an Ir(III) complex into MOFs but also an efficient method for the green synthesis of sulfoxide.