Metal sulfide based materials as photocatalysts for energy conversion are essential to produce value-added chemical fuels, but their intrinsically slow carrier dynamics and low activity are yet to be resolved. Herein, we developed a unique heterogeneously nanostructured ZnIn₂S₄-CdS heterostructure that involves zero-dimensional (0D) CdS quantum dots uniformly confined on three-dimensional (3D) ZnIn₂S₄ nanoflowers, which achieves an excellent catalytic performance of CO₂ photoconversion under visible-light irradiation. The obtained hierarchical heterostructure can significantly enhance the light harvesting, shorten the migration distance of carriers, and obviously accelerate the transport of electrons. As evidenced by the ultrafast transient absorption spectroscopy, the formed interface can effectively facilitate charge separation and transport. This work opens up a new avenue to carefully design the elaborate heterostructures for achieving optimal charge separation efficiency by lowering interfacial kinetic barriers and energy losses at the interface.