Modulating hetero-multimetallic atoms in covalent organic framework for efficient oxidization of olefin compounds

Abstract

Heterogeneous multinuclear catalysts have clear advantages, such as high selectivity, cascading production, and specific chemical transformations, but they are difficult to synthesize due to their high structural complexity. Here, we fabricated crystalline, porous covalent organic frameworks (COFs) with high-density chelating sites by incorporating pyrimidine groups onto their pore wall. Using a molecular coordination imprint strategy, tri-coordination (2N, 1O) and di-coordination (1N, 1O) vacancies were proportionally prepared using Cu(II) ions as templates. Consequently, various hetero-multimetallic assemblies, including Cu(II)/Pd(II), Cu(II)/Fe(III), Cu(II)/Zn(II), and Co(II)/Pd(II), were obtained with tunable ion contents in the range of 3:0 to 3:3 on the COF skeleton. The Cu(II)/Cu(II)/Pd(II)-doped COF sample implemented a sustainable oxidization of olefin compounds, which outperformed all existing catalysts to date for the synthesis of value-added ketone, surpassing 620 times compared with the commercial catalyst (PdCl₂/CuCl₂).