Crosslinked polyethyleneimine‐based structures in different morphologies as promising <scp>CO₂</scp> adsorption systems: A comprehensive study

Abstract Although there are many studies on CO 2 adsorption via PEI‐modified carbon particles, metal–organic frameworks, zeolitic imidazolate frameworks, and silica‐based porous structures, only a limited number of studies on solely cross‐linked PEI‐based structures. Here, the CO 2 adsorption capacities of PEI‐based microgels and cryogels were investigated. The effects of various parameters influencing the CO 2 adsorption capacity of PEI‐based structures, for example, crosslinker types, PEI types (branched [bPEI] or linear [lPEI]), adsorbent types (microgel or cryogel), chemical‐modification including their complexes were examined. NaOH‐treated glycerol diglycidyl ether (GDE) crosslinked lPEI microgels exhibited higher CO 2 adsorption capacity among other microgels with 0.094 ± 0.006 mmol CO 2 /g at 900 mm Hg, 25°C with 2‐ and 7.5‐fold increase upon pentaethylenehexamine (PEHA) modification and Ba(II) metal ion complexing, respectively. The CO 2 adsorption capacity of bPEI and lPEI‐based cryogels were compared and found that lPEI‐GDE cryogels had higher adsorption capacity than bPEI‐GDE cryogels with 0.188 ± 0.01 mmol CO 2 /g at 900 mm Hg and 25°C. The reuse studies revealed that NaOH‐treated GDE crosslinked bPEI and lPEI microgels and cryogels showed promising potential, for example, after 10‐times repeated use &gt;50% CO 2 adsorption capacity was retained. The results affirmed that PEI‐based microgels and cryogels are encouraging materials for CO 2 capture and reuse applications.