Unique porous ZnS-CdS-CoSx Reuleaux triangle nanosheets were prepared via a bimetallic precursor and ion-exchange process, achieving efficient photocatalytic H2 production due to the synergistic effect of Z-scheme heterojunction and vacancy defects. Display omitted •Porous ZnS-CdS-CoSx Reuleaux triangle nanosheets are first reported.•Z-scheme heterojunction and S, Zn vacancies enable efficient charge separation.•CoSx provides abundant S22- species as active sites for H2 production.•Excellent HER rate (53.43 mmol·g−1·h−1) and AQE (30.8 % at 420 nm) are obtained.•Prominent H2-evolving stability attested by cycling and long-term tests. Photocatalytic water-splitting employing Z-scheme semiconductor heterojunction is a promising avenue to realize the efficient conversion and storage of renewable solar energy because of its space-separated reduction and oxidation sites, effective charge separation and transportation, as well as the stronger redox abilities of photogenerated carriers. Nevertheless, the efficiency of Z-scheme photocatalysts is often weakened by the insufficient coupling of components due to the stepwise hybridization processes. In this work, unique ZnS-CdS-CoSx porous Reuleaux triangle nanosheets with intimate Z-scheme hetero-interface and S, Zn vacancies were produced by using Zn2Co3(OH)10·2H2O as the bimetallic precursor for subsequent sulfurization and Cd2+-exchange reaction. Noticeably, such a novel structure shows desirable features which suggest a promising photocatalyst for visible-light photocatalytic H2 evolution, including superior charge-separating capability enabled by the Z-scheme charge transfer and synergetic charge-trapping effect of S, Zn vacancies, excellent light-harvesting capacity, abundant S22− species as H2-evolving active sites, a large surface area, and good stability without obvious decline in activity after multiple cycling and long-term tests. The ZnS-CdS-CoSx heterojunction exhibits an outstanding visible-light-driven H2-evolving activity as high as 53.43 mmol·g−1·h−1, corresponding to a high apparent quantum efficiency of 30.8 % at 420 nm, far better than that of Pt-loaded CdS and a great deal of CdS-based photocatalysts reported in the literatures. The present work may shed new light on the designed synthesis of high-performance semiconductor heterojunction for sustainable solar utilization and environmental remediation.