Synthesis of CdS-decorated MIL-68(Fe) nanocomposites: Efficient and stable visible light photocatalysts for the selective reduction of 4-nitroaniline to p-phenylenediamine in water

Visible-light-initiated organic transformations have received much attention because of low cost, relative safety, and environmental friendliness. In this work, a series of CdS-decorated MIL-68(Fe) nanocomposites (CdS-M68 NCs) have been prepared via a facile room-temperature photodeposition technique in a controlled manner. Importantly, the CdS-M68 NCs exhibit remarkably enhanced photoactivity toward selective reduction of 4-nitroaniline (4-NA) to p -phenylenediamine (PPD) in water under visible light irradiation (λ   ≥   420   nm) as compared to bare CdS and MIL-68(Fe), giving a 4-NA conversion of ∼100% after irradiation for 8   min. The significantly enhanced photoactivity is attributed to the integrated factors of the effective transportation of the photogenerated electron-hole pairs and the enhanced visible light absorption intensity. Combining with trapping experiments and ESR analysis, it could be revealed that the photoexcited electrons and CO 2− radicals should be the main active species in the present system. In addition, a possible photocatalytic reduction mechanism has been investigated.