Metal-Free Heptazine-Based Porous Polymeric Network as Highly Efficient Catalyst for CO₂ Capture and Conversion

The capture and catalytic conversion of CO₂ into value-added chemicals is a promising and sustainable approach to tackle the global warming and energy crisis. The nitrogen-rich porous organic polymers are excellent materials for CO₂ capture and separation. Herein, we present a nitrogen-rich heptazine-based microporous polymer for the cycloaddition reaction of CO₂ with epoxides in the absence of metals and solvents. HMP-TAPA, being rich in the nitrogen site, showed a high CO₂ uptake of 106.7 mg/g with an IAST selectivity of 30.79 toward CO₂ over N₂. Furthermore, HMP-TAPA showed high chemical and water stability without loss of any structural integrity. Besides CO₂ sorption, the catalytic activity of HMP-TAPA was checked for the cycloaddition of CO₂ and terminal epoxides, resulting in cyclic carbonate with high conversion (98%). They showed remarkable recyclability up to 5 cycles without loss of activity. Overall, this study represents a rare demonstration of the rational design of POPs (HMP-TAPA) for multiple applications.