Upcycling paper waste into aminosilane-functionalized cellulose-graphene oxide composite aerogel adsorbents for low-pressure CO₂ capture

The need for efficient materials to reduce CO₂ emissions from anthropogenic activities is critical in addressing global warming. On the other side, waste accumulation in landfills, particularly paper waste, is also a global concern. Office paper contains a high concentration of cellulose, the most abundant biopolymer on the planet, while its abundance in hydroxyl groups allows it to be easily functionalized. In this work, aerogel composites of cellulose with graphene oxide (CGO) were developed for CO₂ adsorption and further functionalized with (3-aminopropyl)triethoxysilane (APTES). The CO₂ adsorption performance of the resulting aerogels was tested at various temperatures (25, 40, and 60 °C) as a function of pressure up to 1 bar. Adsorption kinetics, heat of adsorption, cyclability, CO₂/N₂ selectivity, and water uptake were also evaluated. The CO₂ adsorption capacity of the APTES-grafted CGO composite at 25 °C was 1.2, 1.5, and 2.5 mmol/g at 0.01, 0.1, and 1 bar, respectively, with a CO₂/N₂ selectivity at 0.1 bar of 87. The adsorbents exhibited sustainable performance with minor capacity loss after pressure swing adsorption (PSA), and completely regenerable cyclic performance after temperature pressure swing adsorption (TPSA). This work provides a combined strategy for addressing the dual challenge of CO₂ emissions mitigation and upcycling paper waste.