Atomically Dispersed Cu on Graphitic Carbon Nitride Nanosheets as Catalysts for the Synthesis of Disubstituted Triazoles

The regiospecific, high-yield synthesis of 1,4-disubstituted 1,2,3-triazole via an azide-alkyne cycloaddition reaction is of high practical utility as derivatives of this heterocycle are reported to exhibit diverse biological activities. Herein, we demonstrate the development of atomically dispersed copper atoms on graphitic carbon nitride (g-C3N4/Cu) with up to 30% metal loading through a facile one-pot synthesis involving the thermal decomposition of a precursor mix under controlled atmosphere. The EXAFS results established that Cu is atomically dispersed over the g-C3N4 matrix through C-N coordination. The g-C3N4/Cu catalyst with 20 wt % metal loading afforded a variety of 1,4-disubstituted 1,2,3-triazoles in excellent yields in the presence of triethylamine base at 60 degrees C using water as the reaction medium. The triazole synthesis also proceeded well in the absence of an additional base, presumably due to the amino groups of the g-C3N4 matrix. The prepared catalyst exhibited appreciable cyclic stability (>95% yield over 5 cycles) by virtue of the strong metal-support interaction between Cu atoms and the g-C3N4 matrix, preserving the Cu active sites during the reaction cycles. This study demonstrates the development of ultrahigh-density Cu single atoms on g-C3N4 and provides a greener and sustainable pathway for high-yield azide-alkyne cycloaddition reactions.