High molecular weight polyethylenimine encapsulated into a porous polymer monolithic by one-step polymerization for CO2 capture

Abstract

A novel porous solid amine adsorbent (PEI@polyHIPE) with a highly interconnected pore network was prepared by high inner phase emulsion (HIPE) polymerization of styrene and divinylbenzene, and was simultaneously functionalized with high molecular weight (M_w = 70 000 Da) polyethylenimine (PEI). This proposed route requires fewer chemical reagents and less energy than conventional solid amine adsorbents that were prepared by amine post-modification such as chemical grafting and wet impregnation. The SEM image shows that a PEI layer was formed on the adsorbent's surface without damaging its original structure. And the CO₂ adsorption capacity and pore structure of PEI@polyHIPE could be adjusted by adding different amounts of PEI. The one-step fabricated 4.0PEI70k@polyHIPE adsorbent showed a maximum adsorption capacity of 4.18 mmol CO₂ per g-adsorbent at 20 °C under humid conditions. It obviously exhibited better CO₂ adsorption performance, high amino utilization efficiency, and quick adsorption kinetics compared to PEI post-modification porous polystyrene (polyHIPE-PEI). This was attributed to its well-interconnected hierarchical structure, which could remarkably reduce gas diffusion resistance. Meanwhile, owing to the high-molecular-weight of PEI, the amount of amine loss could decrease during the process of adsorption/desorption, thus the adsorbent of PEI@polyHIPE showed promising regeneration performance. This one-step synthetic route provides a novel strategy for preparing amine functionalized adsorbents with high sorption capacity, amine efficiency, and regeneration stability.