CuI Coordination Polymer‐Catalyzed Azide–Alkyne Cycloaddition Click Reaction at Room Temperature

Framework based compounds for eco‐friendly catalysis is of utmost industrial interest. CuI‐catalyzed “click” reactions are a class of highly efficient and widely used chemical reactions in organic synthesis for potential applications in biotechnology, medicine, polymer, and material sciences. The importance of click chemistry also acknowledge by 2022 Noble Prize in chemistry. One of the most well‐known click reactions is the copper‐catalyzed azide‐alkyne cycloaddition (CuAAC), which is a type of Huisgen 1,3‐dipolar cycloaddition reaction. Herein, three stable copper(I)‐coordination polymers (CPs), [Cu(4‐ABPT)Cl], CP‐1; [Cu(4‐ABPT)Br], CP‐2; [Cu2(4‐ABPT)0.5I2], CP‐3; (4‐ABPT=3,5‐di(pyridine‐4‐yl)‐4H‐1,2,4‐triazol‐4‐amine) have been chosen for CuAAC reaction, due to presence of both Lewis acidic (copper ion), and basic (pyridyl and amine) sites. The counter anion plays a crucial role in their structural motif as well as catalytic efficiency. These easily synthesizable and scalable catalysts exhibit the trend of CP‐1>CP‐2>CP‐3 in catalysis for the selective conversion of phenylacetylene, benzyl bromide, and sodium azide into 1,4‐cycloaddition product within 2 h at ambient temperature and solvent free reaction conditions. CuAAC reaction using catalyst CP‐1 exhibits near quantitative conversion within 2 h at room temperature in solvent free conditions. Herein, we demonstrated the bulk‐scale synthesis of CuI CPs for efficient azide‐alkyne cycloaddition click reaction under mild reaction conditions. The Coordination Polymers possesses CuI Lewis acidic sites as well as basic sites viz. free amine, pyridyl ‘N’ and triazolyl ‘N’ groups. The ‘N's of functional groups may or may not share their lone pairs during bond formation. These basic groups can also easily form intra and inter‐molecular H‐bonds. Needless to say, that these properties will play an important role in applications using these materials.