Single-atom catalysts (SACs) are drawing widespread attention because of high atomic availability, strong metal–support interaction (SMSI), high activity and selectivity. The porous materials are potential supports for anchoring single atoms since their ultrahigh surface areas and homogeneously adjustable channel structure. The SACs stabilized over the porous materials, such as zeolites, metal-organic frameworks (MOFs), carbon nitride (CN) and other mesoporous materials (silica, metal oxides), have been extensively explored nowadays. In this review, we summarize and highlight the latest studies in microenvironment regulation of single atom active centers through a full-scale comparison over porous materials anchored SACs in the advancement of structure characteristics, modulation strategy, characterizations, and reaction implementations. The precise electronic and geometric configurations of isolated metal atoms can be modulated through the strong interaction between the metals and supports of porous materials. Furthermore, recent progress of certain typical catalytic reaction is comprehensively explored to receive in-depth analysis of the catalytic mechanisms over the well-regulated SACs based on advanced techniques. Finally, the principal challenges and outlooks of porous materials supported SACs toward potential catalytic reaction are also suggested and expected. This work will offer novel perspectives on the progression of well distributed catalysts for a series of practical application.

Single atom sites are widely applied in various electrocatalytic fields due to high atom utilization, mass activity, and selectivity. They are limited in catalyzing multi-electron reactions due to their intrinsic mono-metal center feature. Dual atom sites (DASs) as promising candidate have received enormous attentions because adjacent active sites can accelerate their catalytic performance via synergistic effect. Herein, the fundamental understandings and intrinsic mechanism underlying DASs and corresponding electrocatalytic applications are systemically summarized. Different synergy dual sites are presented to disclose the structure–performance relationship with engineering the well-defined DASs on the basis of theoretical principle. An overview of the electrocatalytic applications is showed, including oxygen reduction reaction, hydrogen evolution reaction, oxygen evolution reaction, carbon dioxide reduction reaction, and nitrogen reduction reaction. Finally, a conclusion and future prospective are provided to reveal the current challenges for rational designing, synthesizing, and modulating the advanced DASs toward electrocatalytic reactions.

The appropriate catalysts can accelerate the reaction rate and effectively boost the efficient conversion of various molecules, which is of great importance in the study of chemistry, chemical industry, energy, materials and environmental science. Therefore, efficient, environmentally friendly, and easy to operate synthesis methods have been used to prepare various types of catalysts. Although previous studies have reported the synthesis and characterization of the aforementioned catalysts, more still remain in trial and error methods, without in-depth consideration and improvement of traditional synthesis methods. Here, we comprehensively summarize and compare the preparation methods of the trial-and-error synthesis strategy, structure–activity relationships and density functional theory (DFT) guided catalysts rational design for nanomaterials and atomically dispersed catalysts. We also discuss in detail the utilization of the nanomaterials and single atom catalysts for converting small molecules (H₂O, O₂, CO₂, N₂, etc.) into value-added products driven by electrocatalysis, photocatalysis, and thermocatalysis. Finally, the challenges and outlooks of mass preparation and production of efficient and green catalysts through conventional trial and error synthesis and DFT theory are featured in accordance with its current development.

As an important part of carbon neutralization, carbon dioxide electroreduction reaction (CO₂RR) can convert CO₂ into high value-added chemicals and fuels to realize the recycling of carbon resources and solve the problem of environmental pollution. Therefore, exploring the element species and surface structure of the catalyst plays a central role in improving the performance of the catalyst, enhancing the CO₂ conversion efficiency and forming C₁ and C₂₊ products. Here, we summarize the recent progress in the selective regulation of CO₂RR reaction products by different elements. In particular, we emphasize the structure-property relationship of CO₂RR by the microenvironment of metal center and substrate, heteroatom doping, hydrogen bond network of metal-free polymer, and construction of heterogeneous catalytic system. At the same time, the recent advances for the identification of CO₂RR active sites and mechanistic studies on the process of reducing CO₂ conversion to different products are reviewed, as well as a comprehensive review to the final products. Finally, we outline the inevitable challenges faced by CO₂RR and present our own recommendations aimed at contributing to CO₂ resource utilization.

Catalysts can accelerate the chemical reaction rate and effectively promote the molecules transformation, which is of great significance in the research of chemical industry and material science. The extreme utilization of reactive sites has led to the emergence and development of atomically dispersed materials (ADMs). The highly active coordination unsaturated metal sites and fully utilized metal atoms make ADMs show great potential in catalytic reactions. The adjustment of coordination environment and electronic structure provides more possibilities for constructing reactive centers with different properties. This review summarized the application and research progress of ADMs in different fields. The design strategy and structure–activity relationship of ADMs for specific reactions were summarized and analyzed. Moreover, we also provided advices for the challenges and opportunities faced by ADMs in catalytic reactions.

Metal-based atomically dispersed catalysts have attracted more attention because of their excellent catalytic performance and nearly 100% atom utilization. Therefore, it is very important to comprehensively and systematically understand the relationship between catalytic active sites and catalytic performance at atomic scale. Here, we discuss and summarize in detail the key and fundamental factors affecting the active site, and relate them to the catalytic performance. First, we describe the effectiveness of active site design by coordination effects. Then, the role of chemical bonds in the active sites in changing the reaction performance is discussed. In addition, for intermetallic compounds, we explore how the spacing of active atoms affects the catalytic behavior. Moreover, the importance of synergistic effect in catalyst design is further discussed. Finally, the key parameters affecting the catalytic performance at atomic scale are summarized, and the main challenges and development prospects of atomic catalysts in the future are put forward.

Supported atomically dispersed metal catalysts (ADMCs) have received enormous attention due to their high atom utilization efficiency, mass activity and excellent selectivity. Single-atom site catalysts (SACs) with monometal-center as the quintessential ADMCs have been extensively studied in the catalysis-related fields. Beyond SACs, novel atomically dispersed metal catalysts (NADMCs) with flexible active sites featuring two or more catalytically centers including dual-atom and triple-atom catalysts have drawn ever-increasing attention recently. Owing to the presence of multiple neighboring active sites, NADMCs could exhibit much higher activity and selectivity compared with SACs, especially in those complicated reactions with multi-step intermediates. This review comprehensively outlines the recent exciting advances on the NADMCs with emphasis on the deeper understanding of the synergistic interactions among multiple metal atoms and underlying structure–performance relationships. It starts with the systematical introduction of principal synthetic approaches for NADMCs highlighting the key issues of each fabrication method including the atomically precise control in the design of metal nuclearity, and then the state-of-the-art characterizations for identifying and monitoring the atomic structure of NADMCs are explored. Thereafter, the recent development of NADMCs in energy-related applications is systematically discussed. Finally, we provide some new insights into the remaining challenges and opportunities for the development of NADMCs.

Hydrogen production from water splitting using renewable electric energy is an interesting topic towards the carbon neutral future. Single atom catalysts (SACs) have emerged as a new frontier in the field of catalysis such as hydrogen evolution reaction (HER), owing to their intriguing properties like high activity and excellent chemical selectivity. The catalytic active moiety is often comprised of a single metal atom and its neighboring environment from the supports. Recent published reviews about electric-driven HER tend to classify these SACs by the species of active center atom, nevertheless the influence of their neighboring coordinated atoms from the supports is somehow neglected. Thus we classify the SACs for HER through the type of supports, highlighting the electronic metal–support interaction and their coordination environment from support. Then, we put forward some structural designing strategies including regulating of the central atoms, coordination environments, and metal–support interactions. Finally, the current challenges and future research perspectives of SACs for HER are briefly proposed.

Metal-based electrocatalysts with different sizes (single atoms, nanoclusters, and nanoparticles) show different catalytic behaviors for various electrocatalytic reactions. Regulating the coordination environment of active sites with precision to rationally design an efficient electrocatalyst is of great significance for boosting electrocatalytic reactions. This review summarizes the recent process of heterogeneous supported single atoms, nanoclusters, and nanoparticles catalysts in electrocatalytic reactions, respectively, and figures out the construct strategies and design concepts based on their strengths and weaknesses. Specifically, four key factors for enhancing electrocatalytic performance, including electronic structure, coordination environment, support property, and interfacial interactions are proposed to provide an overall comprehension to readers in this field. Finally, some insights into the current challenges and future opportunities of the heterogeneous supported electrocatalysts are provided.

The oxidation of hydrocarbons to produce high value-added compounds (ketones or alcohols) using oxygen in air as the only oxidant is an efficient synthetic strategy from both environmental and economic views. Herein, we successfully synthesized cobalt single atom site catalysts (Co SACs) with high metal loading of 23.58 wt.% supported on carbon nitride (CN), which showed excellent catalytic properties for oxidation of ethylbenzene in air. Moreover, Co SACs show a much higher turn-over frequency (19.6 h^-1) than other reported non-noble catalysts under the same condition. Comparatively, the as-obtained nanosized or homogenous Co catalysts are inert to this reaction. Co SACs also exhibit high selectivity (97%) and stability (unchanged after five runs) in this reaction. DFT calculations reveal that Co SACs show a low energy barrier in the first elementary step and a high resistance to water, which result in the robust catalytic performance for this reaction.