Dynamic Confinement Approach for High Metal Loading Single‐Atom Catalysts Based on Covalent Organic Frameworks

Abstract Single‐atom catalysts (SACs) offer stable, well‐defined active sites by anchoring individual metal atoms on stable organic or inorganic supports, though achieving high metal loadings without clustering or leaching remains a major challenge. Here, we report a synthetic strategy for developing ultra‐high metal loading SACs based on palladium polyphthalocyanine covalent organic frameworks (COFs) synthesized via a mixed metal ionothermal approach, which involves the cyclization of tetracyanobenzene and tetracyanopyrazine as precursors in molten salt mixtures of PdCl 2 /ZnCl 2 or PdCl 2 /ZnCl 2 /NaCl. This approach effectively combines the formation of crystalline polymeric hosts with metal impregnation in a single step, yielding COFs with atomically distributed Pd ions and metal contents of up to 22.2 wt%. Theoretical simulations reveal that the crystalline framework dynamically confines Pd atoms between different binding sites within the pores, preventing dimerization and ensuring long‐term catalyst stability. The synthesized catalysts were evaluated under continuous flow conditions, exhibiting stable performance with yields as high as 90% and maintaining stability over a 24 h time‐on‐stream under low‐conversion conditions. These results establish a new benchmark for SACs and underscore the importance of dynamic confinement approach in achieving high metal loadings on crystalline organic supports.