In Situ Engineering of Zwitterionic Betaine‐Based Covalent Organic Frameworks Boost Cooperative CO2 Catalytic Conversion

Abstract The development of a privileged organocatalyst featuring well‐defined catalytic sites to drive highly cooperative CO 2 conversion into high value‐added fine chemicals is promising while challenging. Here in this work, three zwitterionic betaine‐based covalent organic frameworks (COFs) bearing sulfonate, carboxylate, and phosphate moieties, namely, PS‐TpBpy, BA‐TpBpy, and PA‐TpBpy, are in situ engineered through the post‐synthetic quaternization of the bipyridine COF (TpBpy). Density functional theory‐based Fukui function indicated that the pyridinium cation and the alkaline O anion in these betaine‐based COFs serve as synergistic electrophilic and nucleophilic active sites, thus simultaneously activating o‐ phenylenediamine and CO 2 for their highly efficient conversion to benzimidazole. Meanwhile, such assembly endows the catalysts with enhanced stability, alkalinity, and hydrophobic microenvironment, facilitating the fast enrichment of phenylsilane and CO 2 , and leading to largely enhanced reaction kinetic rates. In‐depth mechanism investigations manifested that a cooperative double‐catalytic cycle pathway is driven by the zwitterionic betaine‐based COFs, which thermodynamically promote the carbamic acid formation and CO 2 reduction processes, thereby improving the overall catalytic efficiency. This work highlights the rational construction of unique zwitterionic betaine‐based COFs as the bifunctional organocatalysts to boost the highly cooperative CO 2 catalytic conversion thermodynamically and kinetically.