Fast and Reversible Direct CO_2 Capture from Air onto All-Polymer Nanofibrillated Cellulose-Polyethylenimine Foams

摘要

Fully polymeric and biobased CO_2 sorbents composed of oxidized nanofibrillated cellulose (NFC) and a high molar mass polyethylenimine (PEI) have been prepared via a freeze-drying process. This resulted in NFC/PEI foams displaying a sheet structure with porosity above 97% and specific surface area in the range 2.7-8.3 m~2•g~(-1). Systematic studies on the impact of both PEI content and relative humidity on the CO_2 capture capacity of the amine functionalized sorbents have been conducted under atmospheric conditions (moist air with ～400 ppm of CO_2). At 80% RH and an optimum PEI content of 44 wt %, a CO_2 capacity of 2.22 mmol•g~(-1), a stability over five cycles, and an exceptionally low adsorption half time of 10.6 min were achieved. In the 20-80% RH range studied, the increase in relative humidity increased CO_2 capacity of NFC/PEI foams at the expense of a high H_2O uptake in the range 3.8-28 mmol•g~(-1).