One-step Solvent-free Mechanochemical Oxidation of Lignocellulosic Biomass to Cellulose Nanospheres by a Fe-complex

The most abundant biopolymer in nature, lignocellulosic biomass, is often disregarded as agricultural waste, contributing to environmental pollution. Several reports have demonstrated their utilization by generating nanocellulosic materials using multistep harsh treatments involving H2SO4 and NaOH. However, these processes do not reduce the waste generated and release toxic gases into the environment. To address these pressing issues and effectively utilize our bioresources, we herein demonstrate a single-step, solvent-free method to oxidatively degrade lignocellulosic biomass such as corncob waste into completely water-dispersible carboxylate-functionalized cellulose nanospheres (CNS). This process uses an environmental-friendly catalyst (Et4N)2[Fe-(Ph,Me)bTAML] and sodium percarbonate as the oxidant. Our catalyst acts as a combined mimic of LPMO and lignin peroxidase, effectively breaking down the biomass without generating any toxic by-products. We confirmed the reaction mechanism using smaller repeating units like glucose and cellobiose, demonstrating a pathway similar to LPMO and unlike TEMPO-mediated oxidation. Finally, we extended our idea of using the CNS, due to its enhanced surface activity, as an O/W Pickering emulsion stabilizer and used it as a sustainable alternative to commercial detergents.