Phenolic Hydroxyl-Functionalized Covalent-Organic Frameworks for Formal [3+2] Reaction

Covalent-organic frameworks (COFs) are rarely used as heterogeneous catalysts for cycloaddition reactions, especially in [3+2] reactions. In this study, 4,4 ',4 '',4"'-(pyrene-1,3,6,8-tetrayl) tetra-aniline, 2,5-dihydroxyterephthalaldehyde, and 2,5-dimethylterephthalaldehyde are used to construct COFs with high porosity, crystallinity, and chemical stability. The phenolic and methyl groups on the pore channel of the COFs are precisely tuned to effectively serve as heterogeneous catalysts for the formal [3+2] reaction between 5-alkoxyoxazoles and azodicarboxylate or nitrosobenzene compounds. The resultant COFs that are assembled from adjustable building unit ratios exhibit excellent catalytic performance for the targeted [3+2] reaction.