Manipulation of plasmon-induced hot electron transport in Pd/MoO3-x@ZIF-8: Boosting the activity of Pd-catalyzed nitroaromatic hydrogenation under visible-light irradiation

Controlling the charge carrier transfer pathway in a plasmonic catalyst is the key to developing efficient catalyst. Herein, a visible-light responsive plasmonic catalyst is prepared by depositing Pd nanoparticles on ZIF-8 (zeolitic imidazolate framework) coated plasmonic MoO3-x composites (Pd/MoO3-x@ZIF-8). The as-prepared catalyst allows effective plasmon-induced electron transfer from plasmonic MoO3-x to Pd active site by taking advantages of the Schottky junction formed between Pd metal nanoparticles and MoO3-x@ZIF-8 composite as well as heterojunction formed between ZIF-8 and MoO3-x, effectively retarding the recombination of the plasmonic induced hot electron-hole pairs in MoO3-x. As a result, the Pd/MoO3-x@ZIF-8 presents exceptionally higher catalytic activities for the hydrogenation of nitroaromatics under visible-light irradiation than that under dark conditions, which are far superior to those of Pd/MoO3-x and Pd/ZIF-8. The enhanced activity can be attributed to the cooperative promoting effects between Pd nanoparticles and plasmonic MoO3-x@ZIF-8 on facilitating the plasmon-induce electron transfer, and the possible reaction mechanism is proposed. This study expands the scope of reductive organic chemical transformation catalyzed by plasmonic catalysts and sheds light on design of efficient plasmonic catalysts by steering an electron flow to promote the photogenerated electron transfer from plasmonic semiconductor to catalytic active site.