The dissolution and homogeneous processing of lignocellulosic biomass presents a significant challenge for advanced biorefineries. In this work, we firstly investigated the dissolution behavior of corn stover-based lignocellulose in 1,8-diazabicyclo [5.4.0] undec-7-ene (DBU)/CO 2 /DMSO solvent system. The dissolution proportion reached 74.3 % via a two-step procedure, which involved pretreating of corn stover in DBU/DMSO solvent at 140 °C for 4 h, followed by dissolution at 50 °C for 6 h under 5 MPa CO 2 . Furthermore, the solubility of the corn stover can be improved by ball-milling treatment. Rheological behavior revealed that the solution viscosity and the intermolecular interactions decreased following ball-milling treatment. Subsequently, a small amount of wood pulp cellulose was incorporated to produce mechanically robust, fully UV-shielding, and all-biomass composite films. The tensile strength of the composite film containing 50 wt% wood pulp cellulose reached 47 MPa. This study provides significant insights into the development of green dissolution systems for lignocellulose and the development of lignocellulose-based advanced materials.
The facile design and preparation of polyelectrolytes is a frontier topic in the fields of polymer science, energy storage devices and catalysis. Herein, linear water soluble cellulosic poly(protic ionic liquid) (CPIL) electrolytes were facilely and atom economically prepared after the dissolution of cellulose in the newly developed DBU/CO2/DMSO solvent system, followed by the simple addition of succinic anhydride under mild conditions. The DBU not only participated in the dissolution of cellulose as a solvent component, but also acted as an organocatalyst for the acylation reaction of cellulose with succinic anhydride, as well as a cation component in the targeted CPIL electrolytes. The reaction was optimized, and the effect of the reaction conditions on the chemical and physical properties of the CPILs was investigated. And then, as a proof of concept, the CPIL electrolyte aqueous solution was successfully used as the catalytic reaction media for the Knoevenagel condensation reaction. It was found that the reaction was homogeneous at the beginning, and the products could precipitate out from the media with the proceeding of the reaction, thus affording satisfactory filtration yields ranging from 56.7% to 93.8%. The solution properties of the CPIL aqueous solution were primarily investigated towards an in-depth understanding of the catalytic mechanism, by which a synergetic catalytic mechanism of the CPILs was proposed, and the reaction started with a nucleophilic addition reaction, and was then followed by a fast dehydration reaction. Finally, the direct reusability potential of the CPIL aqueous solution after the product filtration was also primarily investigated for the Knoevenagel condensation reaction.
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