Metal halide perovskite nanocrystals (MHP NCs) have attracted much scientific interest in photocatalysis. Various types of MHP photocatalysts have been intensively explored in photocatalytic CO 2 reduction in the past few years. However, some key issues, such as severe charge recombination, low stability, and the origin of products, have created bottlenecks in developing MHP photocatalysts. Therefore, the rational design of MHPs is worthwhile to deepen our understanding of the above issues and develop efficient photocatalysts. This Focus Review highlights the recent advances in MHP photocatalysts regarding design principles toward photocatalytic CO 2 reduction. Various modification strategies are clarified, and an outlook on future challenges and prospects is also provided to point out the possible research directions in MHP photocatalysts. It is anticipated that this Focus Review can provide guidance on the design of MHP-based photocatalysts and help uncover some common issues encountered by the scientific community when studying MHP photocatalysts.

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As an emerged photocatalyst, perovskites have attracted enormous interest in photocatalysis due to their excellent photoelectronic properties. However, most of the photoexcited electron–hole pairs recombine together before they reach the surface of perovskite for photocatalysis. The undesired charge recombination would compete with the surface photocatalytic reaction. Hence, the regulation of charge carriers is essential for improving the photocatalytic performance of perovskites. Herein, the charge transfer dynamics by doping Mn2+ in CsPbCl3 perovskite nanocrystals (NCs) is manipulated and the role of the charge carriers with a prolonged lifetime in photocatalysis is investigated. The photogenerated charge carriers with a prolonged lifetime at both Mn2+ dopants and conduction band (CB) endow Mn:CsPbCl3 NCs with an enhanced photocatalytic activity toward CO2 reduction. The doping strategy provides us with a powerful tool to regulate the charge transfer dynamics in perovskite NCs for photocatalysis. It is believed that the long‐lived charge carriers in perovskite NCs have great potential in promoting charge separation and suppressing charge recombination in solar‐to‐fuel conversions.

Metal halide perovskite nanocrystals (MHP NCs) have attracted great interest for photocatalytic CO2 reduction. However, monodispersed MHP NCs generally possess a halogen-deficient surface and are capped by labile long-chain organic ligands, exhibiting low charge transfer rates to nearby cocatalysts in photocatalytic systems. Conventional methods of removing the surface ligands easily bring new surface defects, leading to serious charge recombination and low photocatalytic performance. Herein, we demonstrate a facile halogen compensation method to obtain high-quality CsPbBr3 NCs with a Br-filled surface toward photocatalytic CO2 reduction. The use of reactive thionyl bromide (SOBr2) not only promotes the stripping of native ligands but also repairs Br vacancies (VBr) on CsPbBr3 NCs. Such a halogen compensation method facilitates the charge transfer from CsPbBr3 NCs to nearby cocatalysts (e.g., g-C3N4), resulting in a high CO/CH4 production rate of 190 μmol g–1 h–1 in photocatalytic CO2 reduction. This work provides a new strategy to simultaneously enhance the surface properties of photocatalysts and build a favorable interface for their charge transfer, showing great potential in the design and application of perovskites NCs for photocatalytic applications.

Halide Perovskite Photocatalysts In article number http://doi.wiley.com/10.1002/solr.202200294, Jin Wang, Zhengquan Li, and co‐workers developed a halide perovskite photocatalyst with long‐lived charge carriers by doping Mn as an electron storage. This work provides an effective strategy to regulate charge transfer pathways and achieve high‐efficient halide perovskite photocatalytic systems.