Revealing the impact of lignocellulosic fractionation on lignin photofunctionality toward materials for solar-powered desalination

Abstract

A powerful one-pot functionalization strategy was developed for the direct transformation of lignocellulose to materials with on-demand photofunctionality. This one-step strategy leveraged the solvent-mediated synergy of “depolymerization, suppression of recondensation, and functionalization” to endow lignin with enhanced photofunctionality while simultaneously achieving efficient fractionation of cellulose and xylan. Tuning the reaction temperature during sugarcane bagasse fractionation (from 100 °C to 140 °C) enabled a preliminary functional conversion of the extracted lignin, shifting its property from UV-shielding to photothermal conversion. The photothermal function originated from the control of the molecular structure of lignin. Organic solvents effectively cleaved the β-O-4 and β–β linkages and inhibited their recondensation, resulting in lignin with a low molecular weight and high phenolic hydroxyl content, which promoted intermolecular π–π stacking. In addition, phenylethanol was grafted onto the lignin side chains during fractionation, further enhancing the intramolecular π–π conjugated system. As a proof-of-concept, a complete biomass-based evaporator was constructed from the engineered lignin, which demonstrated a solar water evaporation rate of 2.08 kg m⁻² h⁻¹ with 94.86% efficiency. This work established a new design blueprint for manufacturing advanced materials directly from raw biomass, advancing the biorefinery paradigm from simple component separation to precise, on-demand functionalization.