Phase separation of co-solvent promotes multiple bio-nanomaterials conversion from natural lignocellulose

Natural lignocellulose is supported by parallel bundles of cellulose (framework) and contains tightly interlaced hemicellulose and lignin. Based on the heterogeneous structure, an acid-catalyzed tetrahydrofuran-water (THF-H2O) co-solvent system was designed for the preparation of multiple bio-nanomaterials from natural lignocellulose, including microfibrillated celluloses (MFCs), lignin nanoparticles (LNPs), and carbon quantum dots (CQDs). In this setting, the phase separation of the co-solvent on the surface of lignocellulose enhanced the component fractionation. 95.6% of lignin with high content of G units was effectively removed from the lignocellulose matrix mainly by cleaving beta-O-4 bonds to form uniformly spherical LNPs via pi-pi interactions. The obtained monodisperse LNPs with the average size of 102 nm contained a low ratio of S/G, relatively high content of C-C linkages and abundant functional groups, which exhibited high stability and application value. Meanwhile, 89.1% of the hemicellulose were hydrolyzed to retain a high content of cellulose in lignocellulose residues. Then the MFCs with slender fibrils of approximately 150 nm in diameter were liberated from the cellulose bundles in lignocellulose residues. The released monomolecular compounds, which served as precursors, were thermally processed for CQDs production. This study integrates three types of lignocellulose-based nanomaterial preparation into an integrated pathway to greatly promote the industrialization process of bionanomaterials.