▎ 摘　　要

Hexamolybdenum (Mo-6) cluster-based compounds namely (Cs2Mo6Br8Br6a)-Br-i and (TBA)(2)(Mo6Br8Br6a)-Br-i (TBA = tetrabutylammonium) were immobilized on graphene oxide (GO) nanosheets by taking advantage of the high lability of the apical bromide ions with oxygen-functionalities of GO nanosheets. The loading of Mo-6 clusters on GO nanosheets was probed by Fourier-transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), high resolution transmission electron microscopy (HRTEM) and elemental mapping analyses. The developed GO-(Cs2Mo6Br8Brxa)-Br-i and GO-(TBA)(2)(Mo6Br8Brxa)-Br-i composites were then used as heterogeneous photocatalysts for the reduction of CO2 under visible light irradiation. After 24 h visible light illumination, the yield of methanol was found to be 1644 and 1294 mu mol g(-1) cat for GO-(Cs2Mo6Br8Brxa)-Br-i and GO-(TBA)(2)(Mo6Br8Brxa)-Br-i, respectively. The quantum yields of methanol by using GO-(Cs2Mo6Br8Brxa)-Br-i and GO-(TBA)2Mo(6)Br(8)(i)Br(x)(a) as catalysts with reference to Mo-6 cluster units presented in 0.1 g amount of catalyst were found to be 0.015 and 0.011, respectively. The role of immobilized Mo-6 clusters-based compounds on GO nanosheets is discussed to understand the photocatalytic mechanism of CO2 reduction into methanol. (C) 2015 Elsevier Ltd. All rights reserved.