Microenvironment Engineering of Covalent Organic Frameworks based Single/Dual-Atom Catalysts toward Sustainable Energy Conversion and Storage

Atomically dispersed catalysts with nearly 100% metal utilization have attracted widespread interest in heterogeneous catalysis, energy storage and conversion. Considering the strong metal-support interactions (SMSI), the support plays a vital role in precise regulating local microenvironment of atomically dispersed metal sites at 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 high porosity, pre-design capability, and tunable structures. In this review, we first classified the types of SA/DA sites in COF based on the numbers and coordination structures of catalytic centers. The microenvironment engineering of mainly involving metal center-ligand in the first coordination shell, the symmetry of coordinating atoms, local electronic structure modulation and site distance effect were unravelled for COFs 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, the COF-based SACs/DACs for applications in energy conversion (electrocatalysis and photocatalysis) and storage (lithium, sodium and potassium-ion batteries) were comprehensively and in-depth highlighted, focusing on revealing the relationship of structure-performance. Finally, the future challenges and prospective insights into COF-based-SACs/DACs were delineated.