An ionic porous organic polymer gel with hydroxide anions as an efficient catalyst for N-formylation of amines and amides with carbon dioxide†

The reduction and functionalization of greenhouse gas CO₂ remain in line with the characteristics of green and sustainable development. In this work, an ionic porous organic polymer gel was prepared through a hydrazone condensation reaction between triaminoguanidine and 1,1′-(p-phenylenedimethylene)bis(4-formylpyridinium) cationic units under mild conditions. A metal ion-free triaminoguanidine- and pyridinium-incorporated porous organic polymer gel (PT-OH) with triple synergistic effects of hydroxide anions, multi-ion activation centers and a porous gel structure was obtained after ion exchange. PT-OH provides excellent functional group tolerance and high activity to achieve the N-formylation reaction of primary amines, secondary amines and amides using phenylsilane as the reducing agent under ambient conditions (room temperature and 1 atm CO₂ pressure). Moreover, PT-OH has chemical stability, is easy to recycle and can be reused 5 times without loss of activity. The material represents an efficient, economical and environmentally friendly heterogeneous metal-free catalytic system, which conforms to the principle of green utilization of CO₂.