Anchoring Ag(I) into Nitro-Functionalized Metal–Organic Frameworks: Effectively Catalyzing Cycloaddition of CO₂ with Propargylic Alcohols under Mild Conditions

Carboxylative cyclization of propargylic alcohols with CO2 is significant in synthetic chemistry, but harsh conditions are often needed according to reported results. Herein, a new stable nitro-functionalized metal–organic framework (MOF) of {[Co3(L)2(bpy)4(H2O)2]·DMF·H2O·bpy}n (1) was fabricated through the solvothermal reaction, which exhibited excellent stability in acid and basic solutions. Owing to the porous structure, unsaturated metal sites, and uncoordinated 4,4′-bpy ligands, 1 can serve as an excellent platform for catalytic applications. Hence, Ag(I) ions were incorporated in 1 through a postsynthetic method, and the as-synthesized Ag-1 catalyst with low metal loading (0.64 mol %) displayed excellent catalytic performance in the chemical fixation of CO2 with alkynols under room temperature and atmospheric pressure. The results of 1H NMR analyses further confirmed that Ag-1 can efficiently activate hydroxyl groups and promote the reaction. Moreover, the turnover frequency (TOF) of the Ag-1 catalyst can reach 262 h–1 in a short period of time, which is a high TOF value among the state-of-the-art MOF-based catalysts for catalyzing cycloaddition of CO2 with propargylic alcohols.