Low Temperature Complexation Approach for Immobilization of Single Copper Atom Catalyst in Stacked Polytriazine for Click Cycloaddition Reaction.

Abstract

A significant research gap in the field of synthesis of single atom catalysts (SACs) is addressed by developing a low-temperature complexation approach to stabilize the single metal atoms on stacked polytiazine matrix (g-C₃N₄) with a good metal loading. Unlike conventional high-energy (400-700 °C) and time-intensive (120-300 min) methods typically used for embedding SACs in g-C₃N₄ matrices, the present synthesis utilizes a facile, microwave-assisted method that operates at a low temperature of 140 °C and completes within 30 min. Comprehensive analysis reveal that complexation of the Cu²⁺/Cu⁺ ions with nitrogen in the polytriazine structure facilitates layer stacking. Specifically, Cu⁺ ions promote sheet formation in co-ordination with two nearby N atoms, while Cu²⁺ ions stabilize the stacked layers of the polytriazine framework through co-ordination with four N atoms. The resulting SAC exhibits a Cu metal loading up to 3.5 wt.%, with a specific surface area (SA_BET) of 330 m² g^-1 and pore size distribution centered at 1.9 and 5 nm. The SAC demonstrates excellent catalytic performance for click cycloaddition reactions under base-free conditions, with a high turnover frequency (TOF) of 120 h^-1, a broad substrate scope, and reusability across seven cycles without detectable Cu leaching, making it a promising SAC for triazole synthesis.