Porous Carbon Nitride Frameworks Derived from Covalent Triazine Frameworks Anchored Ag Nanoparticles for Catalytic CO2 Conversion.

Porous carbon nitride frameworks (PCNFs) with uniform and rich nitrogen dopants and abundant porosity were successfully fabricated through the direct carbonization of the covalent triazine frameworks (CTFs) at different pyrolysis temperatures and used as supports to anchor and stabilize Ag nanoparticles (NPs) for catalytic CO2 conversion. Importantly, the pyrolysis temperature plays a crucial role in the properties of porous carbon nitride frameworks. The material carbonized at 700 degrees C showed the highest surface area and micro- and mesoporous structure with a certain interlayer distance. Taking advantage of their unique surface characteristics, PCNF-supported Ag NP catalysts (Ag/PCNF-T, T=pyrolysis temperature) were prepared by a simple chemical method. A series of characterizations revealed that Ag NPs are embedded in the porous carbon nitride frameworks and confined to a relatively small size with high dispersion owing to the assistance of the abundant surface groups and porous structures. The as-obtained Ag/PCNF-T catalysts, especially Ag/PCNF-700, showed excellent catalytic activity, selectivity, and stability for the carboxylation of CO2 with terminal alkynes under mild conditions. This can be due to the existence of abundant nitrogen atoms and diverse porosity, which resulted in highly efficient catalytic activity and stability.