Efficiently catalytic transfer hydrogenation and fast separation of unsaturated alkene compounds over Pd/UiO-66 under green conditions

Abstract

Stable Pd nanoparticles (Pd NPs) have been uniformly dispersed and immobilized into the metal-organic framework of UiO-66, Pd/UiO-66, by a facile impregnation reduction method. Pd/UiO-66 retains the integrity of the UiO-66 crystal structure and incorporated with ultrasmall Pd NPs(1.70 ± 0.32 nm). Using ammonium formate(AF) as a H-donor and water as solvent under green condition, the optimized 1.16 wt% Pd/UiO-66 catalyst exhibits remarkable activity in the catalytic transfer hydrogenation(CTH) of α-methylstyrene(AMS) into cumin(achieving 99.6% conversion of AMS and almost full selectivity to cumin with an extremely high turnover frequency value 456.7 h−1 at 323.15 K). Pd/UiO-66 also show superior catalytic activity in CTH of unsaturated alkene compounds to saturated compounds with excellent stability and recyclability. Furthermore, the as-formed saturated alkanes can be fast and automatic separated easily from the aqueous catalytic media. This study supplies a general method for immobilizing ultrafine Pd nanoparticles into crystalline MOFs and a “green” path for hydrogenation of unsaturated alkene compounds.