Microenvironment engineering of covalent organic framework based single/dual-atom catalysts toward sustainable energy conversion and storage

Atomically dispersed catalysts with nearly 100% metal utilization have attracted widespread interest for application in heterogeneous catalysis, energy storage and conversion. Because of the strong metal–support interactions (SMSIs), the support plays a vital role in precisely regulating the local microenvironment of atomically dispersed metal sites at the atomic-level, which significantly affects the catalytic activity and selectivity of catalysts. Recently, covalent organic frameworks (COFs) have been emerged as suitable support platforms to anchor single-atom catalysts (SACs) and dual-atom catalysts (DACs), owing to their high porosity, pre-design capability, and tunable structures. In this review, we first classified the types of SA/DA sites in COFs based on the numbers and coordination structures of catalytic centers. Microenvironment engineering mainly involving metal center-ligands in the first coordination shell, the symmetry of coordinating atoms, local electronic structure modulation and the site distance effect was unravelled for COF based single/dual-atom active sites. Then, we systematically summarized the design principles, synthetic strategies and advanced characterization techniques of state-of-the-art COF-based SACs/DACs. Furthermore, COF-based SACs/DACs for applications in energy conversion (electrocatalysis and photocatalysis) and storage (lithium, sodium and potassium-ion batteries) were comprehensively highlighted and discussed in-depth, focusing on revealing the relationship of structure–performance. Finally, the future challenges and prospective insights into COF-based-SACs/DACs were delineated.