Sunlight‐driven catalytic reactions are appealing for resolving energy and environmental problems. Transition metal oxides (TMOs) and chalcogenides (TMCs) comprise one of the most popular categories of photocatalysts, thanks to their high stability, low cost, Earth abundance, and outstanding catalytic activity. Downsizing TMOs and TMCs to 2D materials offers additional opportunities to finely tune their surface, electronic, and catalytic properties. However, 2D TMOs and TMCs fall into a less mature field than other well‐established 2D materials. Less is known about their “form‐to‐function” relationship, and mechanisms for their synthesis await more research. Herein, the progress toward the rational design of layered and nonlayered 2D TMOs and TMCs is summarized, as well as principles to engineer their nanosheets (NSs) into 3D architectures for practical application. The formation mechanisms and crystal growth models of these 2D materials are included. The key factors that determine the electronic, surface structures, and catalytic properties of 2D TMOs and TMCs are examined in particular, which are key considerations in tuning their performance in light absorption, charge carrier transfer/separation, molecule capture and activation, etc. Finally, the present challenges and future research directions in this promising field are illustrated.

Tailoring the reactive oxygen species (ROS) in advanced oxidation processes (AOP) in a controlled manner is essential in chemical synthesis and environmental applications. In this paper, we begin with an...

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Exploitation of atomic‐level principles to optimize the charge transfer on ultrathin 2D heterostructures is an emerging frontier in relieving the energy and environmental crisis. Herein, a facile “topological‐atom‐extraction” protocol is disclosed, i.e., selective extraction of Zn from ultrathin half‐unit‐cell ZnIn2S4 (HZIS) can embed thin In2O3 domain into 1.60 nm thick HZIS layer to create an atomically thin in‐plane In2O3/HZIS heterostructure. Thanks to the optimal distance and capability of charge separation, the in‐plane In2O3/HZIS heterostructure is among the best ZnIn2S4‐based CO2 reduction reaction (CRR) photocatalysts, and indeed demonstrates a significant increase (from 6.8‐ to 128‐fold) in CO production rate compared with those of out‐plane ZIS@In2O3 and out‐plane In2O3‐HZIScalcined heterostructures. Density Functional Theory simulation reveals that whereas the out‐plane heterostructure has a much smaller ∆q of 0.2–0.25 e, the in‐plane heterostructure with “zero distance contact” has an optimal ∆q of 1.05 e between In2O3 and HZIS that induces remarkable charge redistribution on the in‐plane heterojunction interface and creates local electric field confined within the ultrathin layer. The charge redistribution efficiently directs the charge‐carrier separation in S‐scheme photocatalytic system and endows long‐lifetime carrier to CRR active HZIS. The findings demonstrate the strong versatility of engineering atomic‐level heterojunctions for efficient catalysts design.

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