Different weight loadings (2-4.2 wt.%) of ZnS nanoparticles stabilized by cetyltrimethylammonium bromide (CTAB) were deposited on montmorillonite (MMT) in order to investigate the performance of ZnS/MMT nanocomposites in the CO2 photocatalytic reduction. Physicochemical properties of prepared nanocomposites were comprehensively characterized by using nitrogen physisorption, XRD, TEM, DR UV-vis spectroscopy and contact potential difference measurements. The main reaction products in a gas phase were hydrogen and methane. According to the blank test the pristine montmorillonite did not possess any photocatalytic performance. The order in photo catalytic performance of individual ZnS/MMT nanocomposites in CO2 reduction depending on the ZnS loading was following: 3.1 wt.% ZnS > 4.2 wt.% ZnS > 2.0 wt.% ZnS. This trend was explained based on UV-vis, TEM and contact potential difference measurements as follows. The increasing loading of ZnS nanoparticles affects the degree of ZnS nanoparticles agglomeration on MMT and this agglomeration finally influences the properties/behavior within electronic structure of ZnS, correlating with the photocatalytic performance of ZnS/MMT nanocomposites in the CO2 reduction. (C) 2014 Elsevier B.V. All rights reserved.