In recent years, halide perovskite materials have sparked intensive research, including their burgeoning development in the field of photo(electro)chemical catalysis. Halide perovskite materials are based on abundant and low‐cost elements with a rich structural composition and a variety of molecular and morphological dimensionalities. They possess versatile advantages over other photo(electro)catalytic materials owing to the facile adjustment of electronic properties via molecular and compositional engineering. Thus, the rapid development of perovskite photo(electro)catalysts in the past 4–5 years has opened up new opportunities for diverse photo(electro)chemical applications, ranging from photocatalytic organic reactions (e.g., chemical transformations, photopolymerization, and degradation) to solar‐to‐chemical fuel conversion (e.g., water splitting and CO2 reduction). This review aims to provide an up‐to‐date discussion on recent applications of halide perovskite photo(electro)catalytic materials, emphasizing their crystal and morphological dimensionality, synthetic methodologies, heterojunction structures, and fundamental structure‐activity relationships. Furthermore, current challenges and future research directions for the rational design of halide perovskite materials to boost their overall catalytic performance and stability are identified and envisaged respectively.

Chiral metal halide perovskites have emerged as a class of highly intriguing circularly polarized luminescence (CPL)-

into their structure-property relationships. [2] The factors of spacer cations (e.g., structure of anchoring group and chain length) are of key importance in advancing the quality and use of 2D halide perovskites for applications in many optoelectronic fields. [2d,3] Concretely, it is necessary to design the structure of the head amino anchoring group with an appropriate size that matches the inorganic layer pockets. [4] For instance, primary ammonium spacer cations are easier to penetrate into the inorganic layer pockets, whilst secondary, tertiary, and quaternary ammonium cation anchoring groups with stronger steric hindrance may lead to greater octahedral lattice distortions and differences in the emission wavelength. [5] Moreover, if bulky groups (e.g., benzyl group) are attached to the amino anchoring site, the 2D perovskite structure may be easily destabilized. [6] On the other hand, spacer cations with suitable chain lengths could provide great bending flexibility of anchoring groups for defects passivation, thereby improving emission intensity and quantum efficiency. [2d] Apart from single spacer cations, organic cations alloying could also be a powerful tool to tune the structural features of perovskites, where the introduction of an additional cation with proper binding energy facilitates the defects passivation and thus promotes the long-term stability of surface cations. [2a,7] Clearly, the spacer cations serving as essential building blocks play a vital role in stabilizing 2D perovskite materials and enabling tunable electronic structures. More promisingly, the incorporation of spacer cations with extra functionality can further expand the application in other areas.Recently, the remarkable combination of valuable characteristics of 2D metal halide perovskites and unique features of chirality motivates intensive exploration of emerging chiral 2D halide perovskite-based materials in circularly polarized luminescence (CPL) photodetectors, circularly polarized lightemitting diodes (LEDs), and spintronic applications. [8] 2D chiral perovskites can be conveniently crafted via utilizing chiral organic spacer cations, which introduce chirality to the system. [9] In addition to the promising optoelectronic properties (e.g., tunable band gap, strong quantum confinementThe combination of unique features of chirality and promising attributes of 2D halide perovskites opens an enticing avenue for the rational design of chiral materials in chiroptoelectronics and spintronics. Despite several impressive approaches available to prepare 2D perovskites with chirality, it poses significant challenges to having a general route to a myriad of highquality nanoscale 2D chiral perovskites with tunable and enhanced chiroptical properties. Herein, a robust spacer cation alloying strategy to craft 2D chiral perovskite nanosheets (NSs) is reported, exhibiting a markedly improved circular dichroism signal over the pure chiral cation-based counterparts. The experimental studies and density functional theory (DFT) modeling r...

Two-dimensional (2D) perovskites have gained tremendous research interest in optoelectronic applications thanks to their structural diversity and superior environmental stability. The advancement of perovskite solar cells (PSCs) using 2D perovskites...