Rational Design and Controlled Synthesis of MOF-Derived Single-Atom Catalysts

Abstract

Single-atom catalysts (SACs) represent a transformative advancement in heterogeneous catalysis, offering unparalleled opportunities for maximizing atomic efficiency and enhancing performance. SACs are characterized by isolated metal atoms uniformly dispersed on suitable supports, ensuring each metal atom serves as an independent catalytic site. This dispersion mitigates metal atom aggregation, a common issue in conventional nanocatalysts, thus enabling superior activity, selectivity, and stability. Metal–organic frameworks (MOFs) have emerged as an ideal platform for SAC synthesis due to their structural diversity, tunable coordination environments, and high surface areas. MOFs provide well-defined coordination sites that facilitate the precise stabilization of single metal atoms, presenting significant advantages over traditional supports like metal oxides and metal materials. Carbonization of MOFs yields MOF-derived carbon materials that retain key structural characteristics while offering enhanced electrical conductivity and stability, making them suitable for various catalytic applications.

Recent advances in the rational design and controlled synthesis of MOF-derived SACs have significantly improved their performance in electrocatalytic processes such as the oxygen reduction reaction (ORR) and carbon dioxide reduction reaction (CO₂RR). However, challenges remain, including maintaining structural integrity during high-temperature carbonization, enhancing mass and electron transport and ensuring the stability of isolated metal atoms under reaction conditions. To address these challenges, strategies such as using structure-directing agents to stabilize MOF frameworks, forming high-energy porous carbon networks, and optimizing support morphologies have been developed to maximize active site exposure and accessibility. On the other hand, the interplay between active metal sites and their coordination environments is crucial in determining the catalytic activity and selectivity of SACs. Advanced computational modeling, coupled with experimental validation, has provided insights into the electronic structure of SACs and the interactions between metal atoms and supports. These insights have enabled researchers to fine-tune local atomic coordination, leading to significant enhancements in performance. For instance, modifying the coordination environment of metal atoms optimizes the binding strength of reaction intermediates, thereby improving both activity and selectivity. This account highlights our group’s contributions to MOF-derived SACs, focusing on innovative design, functionalization, and synthesis approaches that enhance catalytic activity. Notable strategies include using structure-directing agents to maintain pore connectivity during carbonization, preserving high surface areas, and enhancing mass transport. We also discuss the design of high-energy MOF-derived porous carbon networks that facilitate continuous electron transport and improve the interaction between active sites and reactants, ultimately boosting catalytic efficiency. Techniques such as electrospinning have also been employed to create hierarchical porous structures and one-dimensional nanofibers, enhancing mass transport and electron transfer. The rational design of SACs requires a comprehensive understanding of the microenvironment surrounding active sites, and by leveraging computational and experimental tools, researchers can precisely control these microenvironments to achieve desired outcomes.

MOF-derived SACs hold substantial promise for energy conversion and chemical synthesis. Continued research is essential to optimize their design, improve scalability, and explore new applications, ultimately advancing sustainable catalysis. This account provides an overview of the latest advancements in MOF-derived SACs, highlighting their potential as next-generation electrocatalysts and their role in sustainable energy technologies.