Direct conversion of hemicellulose in biomass to functional diformylxylose with a recyclable organic co-solvent

A viable biorefinery platform requires the effective conversion of biomass’s components (cellulose, lignin, and hemicellulose) into high-value chemicals, biofuels, and building blocks for functional materials. High selectivity and efficacy are guiding the development of approaches for direct conversion of biomass. Here, we propose a recyclable co-solvent system of formic acid (FA) and formaldehyde (FH) as the fraction medium allowing to control the excessive degradation of the fractionated hemicellulosic sugars. The co-solvent extraction system of FA/FH significantly promoted the selective extraction of hemicelluloses and in situ converted the xylose into diformylxylose alongside the acid hydrolysis. When a co-solvent extraction with the FA/FH ratio of 3:1 was applied, 90.15 % of xylan in bamboo was extracted and 82.83 % of the extracted xylose was eventually recovered as diformylxylose. Whereas only 48.18 % of xylose was remained under the same conditions without formaldehyde. Moreover, the fractionated diformylxylose (liquid fraction) was directly applied as a bio-based surface coating to paper substrate via hot-pressing and its functionality to improve the hydrophobicity of the treated fiber surface was confirmed. This directional conversion strategy opens a window to selectively extract and recover hemicelluloses fraction as a bio-based functional materials. • A recyclable co-solvent system was applied to biomass fractionation. • Excessive degradation of hemicellulosic sugars was effectively controlled. • 82.83 % of the extracted xylose was eventually recovered as diformylxylose. • The diformylxylose was directly applied as a functional bio-based surface coating. • New strategy provides a huge convenience for the valorization of hemicelluloses.