Magnetically recyclable vanadium-substituted phosphotungstic acid in a deep eutectic solvent for effective wheat straw fractionation

A magnetically recyclable polyoxometalate (POM) catalyst-assisted deep eutectic solvent (DES) system was developed to effectively fractionate wheat straw, promote enzymatic saccharification of the carbohydrate fraction, and valorize the lignin fraction. With the introduction of POM to the benzyl triethylammonium chloride/lactic acid DES system, 86.70% lignin and 91.22% xylan were fractionated from wheat straw at 120 °C for 2 h, while glucan was well retained in the biomass (93.81%). Effective deconstruction of the recalcitrant cell wall structure of wheat straw made a significant enhancement in the glucan digestibility of pretreated biomass to 97.20%. POM/DES-fractionated lignin showed high purity (∼98%), low polydispersity (1.55), and well-preserved β-O-4 structure (35.80/100 Ar), beneficial for its subsequent utilization processes. Importantly, the POM/DES system was readily recycled through a simple magnetic method and exhibited excellent recycling performance in five cycles. This study presented a green DES fractionation process assisted by a readily recyclable magnetic POM catalyst for accomplishing a sustainable and integrated biomass valorization strategy.