Surface and interface atomic engineering of ultrathin 2D inorganic materials for small molecule photocatalysis

Ultrathin two-dimensional (2D) inorganic materials, characterized by their exceptionally high specific surface areas and tunable electronic structures, have emerged as ideal platforms for advancing small-molecule photocatalysis. Yet, the intrinsic limitations of pristine 2D materials - such as rigid band structures and catalytically inert surface sites - often restrict their practical photocatalytic efficiency. Strategic atomic-level modification therefore becomes imperative to unlock their full potential. This review systematically classifies modification strategies for ultrathin 2D materials into two complementary paradigms: surface atomic engineering, which focuses on charge localization and active-site optimization, and interface atomic engineering, which facilitates directional charge transfer and heterojunction-enabled carrier separation. Through a synergistic combination of theoretical simulations and advanced experimental techniques, we first elucidate how these approaches precisely tailor the electronic landscapes of ultrathin 2D materials. We then critically examine their impact on the activity and selectivity of four key photocatalytic small-molecule transformations: H₂O splitting, CO₂ reduction, alkane conversion, and N₂ fixation, offering strategic insights for overcoming reaction-specific bottlenecks. Furthermore, we highlight state-of-the-art in situ characterization methods that establish structure-activity correlations under working conditions. Looking forward, we outline transformative prospects in the field, including big-data-assisted design of surface/interface architectures, next-generation multiscale simulation frameworks, and scalable flow-reactor technologies. These pathways aim not only to deepen the fundamental understanding of photocatalytic mechanisms, but also to accelerate the transition of ultrathin 2D photocatalysts from laboratory innovation toward real-world solar-fuel and chemical production.