Design of Novel Eco-Friendly Lightweight Cellulose/Lignin/PVA Composite Xerogels with Superior Thermal Insulation, Flame Retardancy and CO2 Capture

Abstract

Escalating global temperatures driven by unchecked CO2 emissions, inefficient waste management, and deforestation have intensified the search for sustainable, multifunctional building materials capable of addressing energy efficiency, fire safety, and carbon mitigation simultaneously. In this article, we report a novel bio-based xerogel that combines excellent thermal insulation, outstanding flame-retardancy, and significant CO2 adsorption, offering a practical and eco-friendly solution in one innovative material. The xerogel was carefully engineered using cellulose nanofibers (CNFs), lignin, and polyvinyl alcohol (PVA), crosslinked with glutaraldehyde (GA). Diammonium phosphate (DAP) was added to impart flame resistance, while diethylenetriamine (DETA) synergistically enhanced structural integrity and CO2 capture. The resulting xerogel exhibited high porosity (96.1%), low density (30.1 mg/cm³), and excellent compressive strength (569.3±14 kPa). The compressive strength was found to be 308% higher than that of the neat CNF-xerogels (139.4 ± 11 kPa). It also demonstrated superior thermal insulation (27.6 mW/m.K), 18.1% higher than CNF-xerogels (33.7 mW/m.K), and remarkable fire resistance, outperforming many commercial insulators and recently reported aerogels/xerogels. In CO2 adsorption tests, the xerogel achieved a high capacity of 3.09 mmol/g and maintained over 98.6% regeneration efficiency across six cycles. To the best of our knowledge, this work presents the first bio-based xerogel that simultaneously addresses thermal insulation, fire safety, and CO2 capture, offering a promising pathway toward advanced green materials and circular sustainability.