Phosphorylated/amine-impregnated cellulosic paper for direct CO2 capture

A scalable papermaking process was employed herein to manufacture cellulosic papers from native and phosphorylated cellulose microfibers (referred to as CMF and PCMF, respectively) impregnated with polyethyleneimine (PEI) for Direct Air Capture (DAC) applications. These papers were analyzed in terms of their physico-chemical properties using several techniques. The impact of PEI content on desorbing the co-adsorbed H2O and CO2 from the air, as well as on the anisotropic microporous network, was explicitly analyzed. The results indicated that phosphorylation promotes the uptake of both CO2 and H2O in the corresponding neat and PEI-loaded papers, reaching a superior CO2 adsorption capacity of ∼0.7–0.9 mmol·g−1 for PCMF papers versus 0.07–0.3 mmol·g−1 for CMF papers. Furthermore, the CMF and PCMF papers exhibited H2O adsorption capacities in the range of 1.5–1.8 mmol·g−1 and 2.2–3.8 mmol·g−1, respectively. This work further highlights the combined role of phosphorylation and favorable PEI impregnation in tuning the cellulose CO2 adsorption properties under humid conditions, facilitating the rapid release of the adsorbed CO2 under mid conditions.