Polyethylenimine-Grafted HKUST-Type MOF/PolyHIPE Porous Composites (PEI@PGD-H) as Highly Efficient CO₂ Adsorbents

Searching for highly efficient and robust CO2 adsorbents is very important for CO2 capture, utilization, and storage. In this study, new polyethylenimine-grafted metal–organic framework (MOF)–polymer composites, abbreviated as PEI@PGD-H, were synthesized via high internal phase emulsion (HIPE) template polymerization of divinylbenzene and glycidyl methacrylate, followed by in situ generation of HKUST-type MOF in the presence of hydrophobic-modified CuO nanoparticles via the reaction of CuO with 1,3,5-benzenetricarboxylic acid and then polyethylenimine (PEI) functionalization via epoxy–amine reaction and amine–metal sites interaction. The coexistence of the hierarchical interconnected porous skeleton of poly­(glycidyl methacrylate–divinylbenzene) (PGD), high specific surface area of MOF, and chemical CO2 adsorption of PEI endows PEI@PGD-H with high CO2 adsorption capacity, rate, and selectivity. PEI70@PGD-H shows a CO2/N2 separation factor as high as 76 and CO2 adsorption capacities of 4.3, 3.0, and 1.8 mmol of CO2/g from pure CO2, simulated flue gas, and air, respectively. After 20 CO2 adsorption–desorption cycles, the adsorbent still retained a high and stable CO2 capture capacity over 2.8 mmol of CO2/g for simulated flue gas. The adsorbent also displays reasonably good thermal stability, excellent water endurance, low desorption energy, and easy shaping. The desorption heat is as low as 48 kJ/mol of CO2. These features make PEI@PGD-H highly efficient, robust, and low-energy CO2 adsorbents for practical application in CO2 capture