Nitrogen-rich diaminotriazine-based porous organic polymers for small gas storage and selective uptake

A series of new nitrogen-rich aminal-linked porous organic polymers (APOPs) has been constructed by cost-effective and simple condensation reactions between diaminotriazine-based tectonics and benzaldehyde. The facile and one-pot approach suggests a platform to incorporate functional groups in their pores to tune the affinity between gas molecules and the frameworks. Due to the chemical functionalization and nitrogen-rich pore surface, the APOPs with a moderate specific surface area (S_BET = 724–1402 m² g⁻¹) exhibit significant gas adsorption and high isosteric heats of adsorption (CO₂: up to 4.54 mmol g⁻¹ at 273 K and 1 bar, 33.3 kJ mol⁻¹; H₂: up to 8.95 mmol g⁻¹ at 77 K and 1 bar, 9.4 kJ mol⁻¹). The isosteric heats of adsorption (Q_st) can be tuned by the selection of polar group functionalized building blocks, and their values can be enhanced from 26.6 to 33.3 kJ mol⁻¹ for CO₂, while the increasing of Q_st is beneficial for flue gas separation. Indeed, the strong affinity for CO₂ within the APOPs gives rise to a higher CO₂ uptake at low pressures (0.15 bar) along with good selectivity over N₂.