Exerting charge transfer to stabilize Au nanoclusters for enhanced photocatalytic performance toward selective oxidation of amines

Atomically precise gold nanoclusters have received increasing attention in photocatalysis but suffered from self-oxidation coalescence induced by photo-generated holes. Herein, we report an efficient charge engineering strategy to improve the photo-oxidation activity and stability of Au25(PPh3)10(SC3H6Si(OC2H5)3)5Cl2 nanocluster (AuNC) taking advantage of Z-scheme AuNC/ultrathin BiOCl nanosheets (2D-BiOCl) heterojunction for visible light oxidative self-coupling of amines. The turnover frequency (TOF) over AuNC/2D-BiOCl for benzylamine can reach 1916 h―1, much higher than that of most previously reported gold catalysts with a TOF usually less than 500 h―1. Moreover, the heterojunction can be stabilized for six cycles with the intact structure of AuNC remained. The enhanced photocatalytic activity of AuNC/2D-BiOCl was predominantly attributed to the formation of Z-scheme heterojunction, which effectively accelerated the transfer and separation of photo-generated carriers. Especially, the consumption of holes in AuNC by injected electrons from 2D-BiOCl can inhibit the self-oxidation of AuNC, thus improve its stability. This study provides some insights into the design of metal nanocluster catalysts with Z-scheme charge transfer for the application of photocatalysis.