Porous amino acid-functionalized poly(ionic liquid) foamed with supercritical CO2 and its application in CO2 adsorption

Abstract Design and synthesis of porous materials as efficient CO2 adsorbents have attracted much attention to alleviate the environmental issues derived from CO2 emission. Here a new amino acid-functionalized poly(ionic liquid) poly[1-(p-vinylbenzyl)-3-methylimidazolium glycinate] [P([VBMI][Gly])] was prepared with [VBMI][Cl] and P([VBMI][Cl]) as intermediate products. Chemical structures of the above materials are confirmed by NMR and FT-IR spectra. P([VBMI][Gly]) presents dense monolith with amorphous structure and high thermal stability. CO2 adsorption capacity of P([VBMI][Gly]) is 104 mg CO2/g PIL. To further improve CO2 adsorption performance, porous-P([VBMI][Gly]) was constructed via supercritical foaming technology for the first time. The effects of foaming conditions on the morphology and CO2 adsorption performance of porous-P([VBMI][Gly]) were investigated. And porous-P([VBMI][Gly]) foamed at 110 °C, 30 MPa and 2 h presents uniform cell distribution and obvious porous structure. CO2 adsorption capacity of porous-P([VBMI][Gly]) can reach up to 165 mg CO2/g PIL, which is significantly higher than that of pristine P([VBMI][Gly]). Compared with pristine P([VBMI][Gly]), the pore parameters of porous-P([VBMI][Gly]) are obviously improved, and the porosity and average pore diameter can reach 82.9% and 3 μm respectively. Its CO2 adsorption capacity decreases by 25% after twelve-cycle adsorption–desorption experiments.