Au nanoparticles-anchored defective metal–organic frameworks for photocatalytic transformation of amines to imines under visible light

Abstract

Designing efficient metal organic frameworks (MOF)-based photocatalysts has recently attracted wide attention. In this work, Au nanoparticles(NPs)-decorated defective DUT-67(Zr) (Au@DUT-67(Zr)) with enlarged channels was successfully fabricated and achieved 7.5 times higher conversion than Au NPs-decorated UiO-66(Zr) (Au@UiO-66(Zr)) for photocatalytic selective oxidation of amines to imines driven by visible light. Au NPs are more effectively fixed on DUT-67(Zr) due to its partially hollow structure. Au@DUT-67(Zr) possesses more active sites including unsaturated Zr atoms and oxygen vacancies (VO) than Au@UiO-66(Zr). In situ Fourier transform infrared (FTIR) spectrum reveals that benzylamine is activated on unsaturated Zr sites via HN…Zr species, facilitating deprotonation of –CH2 in benzylamine. VO can not only adsorb and activate oxygen (O2) but also capture plasmonic hot electrons, enhancing the forming of superoxide radical (O2−). Plasmonic hot holes assisted with O2− effectively achieve the selective oxidation of benzylamine. Finally, a possible synergetic mechanism combining the plasmon with the molecular activation is presented to illustrate the photocatalytic pathway at the molecular level.