Rational Design and Fabrication of Nitrogen-Enriched and Hierarchical Porous Polymers Targeted for Selective Carbon Capture

Herein we present a rational design and fabrication of nitrogen-enriched hierarchical porous polymer networks by direct use of polyethylenimine (usually loaded on porous supports) as the building block. Gas adsorption is mainly dependent on the adsorption temperature and pressure. Therefore, adsorption of CO₂, CH₄, and N₂ was performed by varying adsorption temperature (273 and 298 K) and pressure (up to 1 bar). The fabricated polymer networks demonstrate the remarkable CO₂ uptake capacity and selective separation of CO₂ over N₂ and CH₄. Owing to specific acid-base interaction of nitrogen-enriched polymers with acidic CO₂ and the molecular sieving effect of hierarchical pore structure in polymer networks, good CO₂ uptake (199 mg·g^-1) and superior selectivity of CO₂/N₂ (411) and CO₂/CH₄ (107) is observed at 273 K. The adsorption capacities and selectivities obtained in the present work are obviously higher than the reported functional benchmark adsorbents PCTF-1 (143.0 mg·g^-1), PECONF-3 (145.2 mg·g^-1) and UiO-66-NH₂ (171.6 mg·g^-1) as well as recently reported carbon-based and metal-organic framework adsorbents under analogous conditions. Moreover, perfect recyclability is observed without loss in 10 successive cycles with mild regeneration conditions. Thus, good CO₂ uptake and superior CO₂/N₂ and CO₂/CH₄ selectivities with perfect reusability for successive CO₂ capture make hierarchical porous polymers a promising candidate for selective CO₂ separation from various gas mixtures.