Ultrafine Ag Nanoparticles Encapsulated by Covalent Triazine Framework Nanosheets for CO₂ Conversion

This paper describes the fabrication of covalent triazine framework nanosheet-encapsulated Ag nanoparticles (Ag⁰@CTFN) via a simple combination of the ultrasonic exfoliation and solution infiltration method. The as-prepared Ag⁰@CTFN displays an order layered-sheet structure with abundant micropores and mesopores, whereas ultrafine Ag nanoparticles are confined and stabilized in their interlayers through the interaction between N sites of triazine units and Ag nanoparticles. Considering that the Ag⁰@CTFN possesses the merits of high nitrogen, low density, and abundant basic sites, it was thus believed to have enough abilities to adsorb and activate CO₂ in the CO₂ conversion and catalysis. Importantly, the Ag⁰@CTFN, as a heterogeneous catalyst, showed highly catalytic activity in the carboxylation of various alkynes with CO₂ at ambient pressure and low temperature. This catalyst also exhibited good functional group tolerance and excellent stability without any significant loss of its activity after six recycles. This work not only achieves valuable and novel composite material but also provides the first application of covalent triazine framework nanosheets in chemical conversion of CO₂, opening a new field in preparing recyclable heterogeneous catalysts to accelerate the utilization of CO₂.