In the past decade, metal‐halide perovskites have attracted increasing attention in optoelectronics, due to their superior optoelectronic properties. However, inherent instabilities of conventional three‐dimensional (3D) perovskites over moisture, heat, and light remain a severe challenge before the realization of commercial application of metal‐halide perovskites. Interestingly, when the dimensions of metal‐halide perovskites are reduced to two dimensions (2D), many of the novel properties will arise, such as enlarged bandgap, high photoluminescence quantum yield, and large exciton binding energy. As a result, 2D metal‐halide perovskite‐based optoelectronic devices display excellent performance, particularly as ambient stable solar cells with excellent power conversion efficiency (PCE), high‐performance light‐emitting diodes (LEDs) with sharp emission peak, and high‐sensitive photodetectors. In this review, we first introduce the synthesis, structure, and physical properties of 2D perovskites. Then, the 2D perovskite‐based solar cells, LEDs, and photodetectors are discussed. Finally, a brief overview of the opportunities and challenges for 2D perovskite optoelectronics is presented.

The bionic “MoFe cofactor” in 2D Fe–MoTe₂ effectively facilitates the transport and separation of photogenerated carriers by one- and two-electron redox reactions.

The use of single-atom catalysts is a promising approach to solve the issues of polysulfide shuttle and sluggish conversion chemistry in lithium−sulfur (Li−S) batteries. However, a single-atom catalyst usually contains a low content of active centers because more metal ions lead to generation of aggregation or the formation of nonatomic catalysts. Herein, a 2D conductive metal−organic framework [Co 3 (HITP) 2 ] with abundant and periodic Co−N 4 centers was decorated on carbon fiber paper as a functional interlayer for advanced Li−S batteries. The Co 3 (HITP) 2 -decorated interlayer exhibits a chemical anchoring effect and facilitates conversion kinetics, thus effectively restraining the polysulfide shuttle effect. Density functional theory calculations demonstrate that the Co−N 4 centers in Co 3 (HITP) 2 feature more intense electron density and more negative electrostatic potential distribution than those in the carbon matrix as the singleatom catalyst, thereby promoting the electrochemical performance due to the lower reaction Gibbs free energies and decomposition energy barriers. As a result, the optimized batteries deliver a high rate capacity of over 400 mA h g −1 at 4 C current and a satisfying capacity decay rate of 0.028% per cycle over 1000 cycles at 1 C. The designed Co 3 (HITP) 2 -decorated interlayer was used to prepare one of the most advanced Li−S batteries with excellent performance (reversible capacity of 762 mA h g −1 and 79.6% capacity retention over 500 cycles) under high-temperature conditions, implying its great potential for practical applications.

In this work, CDs@Eu-UiO-66(COOH)2 (denoted as CDs-F2), a fluorescent material made up of carbon dots (CDs) and a Eu3+ functionalized metal–organic framework, has been designed and prepared via a post-synthetic modification method. The synthesized CDs-F2 presents dual emissions at 410 nm and 615 nm, which can effectively avoid environmental interference. CDs-F2 exhibits outstanding selectivity, great sensitivity, and good anti-interference for ratiometric sensing Cu2+ in water. The linear range is 0–200 µM and the limit of detection is 0.409 µM. Interestingly, the CDs-F2’s silicon plate achieves rapid and selective detection of Cu2+. The change in fluorescence color can be observed by the naked eye. These results reveal that the CDs-F2 hybrid can be employed as a simple, rapid, and sensitive fluorescent probe to detect Cu2+. Moreover, the possible sensing mechanism of this dual-emission fluorescent probe is discussed in detail.