Facet engineering has played a crucial role in influencing the fundamental properties of conventional semiconductor nanocrystals, including their surface structures and charge carrier dynamics. However, facet control in zero-dimensional colloidal CsPbBr₃ perovskite nanocrystals (PNCs) remains much less explored, primarily owing to the absence of precise synthetic methodologies. Typically, PNCs are predominantly enclosed by {100} facets under thermodynamic control. This work reports the synthesis of gradient-truncated CsPbBr₃ PNCs with exposed non-{100} facets, in which the truncation degree can be precisely modulated by introducing sulfide ions (S²⁻) as regulators. The added S²⁻ ions bind to surface Pb²⁺ sites in PNCs and suppress the closure of high-energy non-{100} facets during the synthesis, thereby regulating the exposure of these facets. These gradient-truncated products exhibit enhanced CO selectivity for photocatalytic CO₂ reduction, with the selectivity showing a positive correlation with truncation degree. The photocatalytic selectivity is attributed to the disparity in adsorption energies of reduction products on {110} facets and the enrichment of photogenerated electrons driven by facet polarity.

Carbon dioxide (CO₂) is a principal greenhouse gas with a substantial impact on global climate change. The photocatalytic reduction of CO₂ represents an economically viable and environmentally benign approach. This technique involves the catalysis of the reaction between CO₂ and epoxides under photocatalytic conditions to yield cyclic carbonates. Notably, this process has garnered significant attention due to its high atomic efficiency and alignment with green chemistry principles. Increasingly, photocatalysts are employed to facilitate the synthesis of cyclic carbonates, demonstrating outstanding performance even under natural light. This review evaluates the current state of research on the photocatalytic cycloaddition of CO₂ with epoxides, analyzes the reaction mechanism and key influencing factors, and provides a comparative summary of the photocatalysts developed in this domain. Additionally, this paper underscores the significance of the reaction devices. The paper explores reaction devices with potential applications for photocatalytic CO₂ and epoxides and envisions future integrations of CO₂ photocatalytic cycloaddition reactions with advanced reaction devices for practical applications in this area.