Crystal Facet‐Engineering of Metal Halide Perovskite Photocatalysts: Progress and Perspectives

ABSTRACT Metal halide perovskites (MHPs) have emerged as promising photocatalysts owing to their exceptional optoelectronic properties, yet suffer from rapid charge recombination, sluggish surface kinetics, and instability. Facet engineering, the controlled exposure of specific crystallographic planes, offers an atomic‐level strategy to tailor surface properties and address these challenges. This review systematically summarizes recent advances in the facet engineering of MHP photocatalysts. It begins with the fundamental principles of how facets govern light harvesting, charge separation, surface reactions, and stability. Key synthetic strategies for facet control are then outlined, followed by a critical discussion on enhanced photocatalytic performance in CO 2 reduction, H 2 evolution, and organic transformations. The synergy of facet engineering with heterojunctions, doping, and defect engineering is also highlighted. Finally, challenges and future perspectives are presented, focusing on stability, precise facet control, high‐index facets, lead‐free perovskite systems, and advanced in situ characterization. This review aims to guide the rational design of efficient and stable MHP photocatalysts through facet manipulation for solar energy conversion and environmental remediation.