Triaminoguanidine-based ionic hydrazone gels for catalyzed formylation of amines with carbon dioxide

Abstract

The development of efficient, economic and heterogeneous catalysts to effectively reduce carbon dioxide into value-added products keeps an effective solution to build a sustainable society. Herein we report ionic porous organic polymer gels via hydrazone condensation reaction using triaminoguanidine cationic units and 1,3,5-benzenetricarbaldehyde as precursors under mild conditions. Ionic hydrazone gel (TB-OH) is obtained through ion exchange. The resulting TB-OH gel is catalytically active due to the synergistic effects of hierarchically porous structure, triaminoguanidine cationic activation centers and hydroxide anions. TB-OH is used as an efficient metal-free, halogen-free heterogeneous catalyst that achieves the formylation of various amines with CO2 to give formamides under ambient conditions. The gel catalyst is stable in the catalysis, is easy to separate, and can be reused for at least 5 cycles. TB-OH thus shows potential application in the catalytic conversion of CO2 because of its low cost, easy acquisition, excellent catalytic performance and easy recycling characteristics.