NDHPI-Functionalized Cu–Co Bimetallic MOF as an Efficient Recoverable Solid Catalyst for Solvent-Free Aerobic Oxidation of Styrene

Selective aerobic oxidation of styrene to value-added oxygenated products remains challenging because of the limited activity and difficult recovery of many homogeneous catalysts. Herein, an N,N′-dihydroxypyromellitimide (NDHPI)-functionalized Cu–Co bimetallic metal–organic framework (MOF), denoted NDHPI/Cu1–Co3–MOF, was constructed through an impregnation strategy to combine NDHPI-derived oxidation activity with accessible sites in a recoverable porous solid. Structural characterization supported the incorporation of NDHPI without loss of the principal crystalline features of the framework. Under the optimized conditions, the material afforded 81.94% styrene conversion with 73.5% selectivity toward styrene oxide at 80 °C under continuous molecular-oxygen supply and solvent-free conditions. The composition- and loading-dependent activity trends support complementary material-level contributions from the introduced NDHPI species and the mixed Cu/Co environment. In one sequence of four consecutive uses, styrene conversion decreased from 81.94% to 64.28%, while styrene oxide selectivity changed from 73.50% to 70.17%.