Novel diacid–superbase ionic liquids for efficient dissolution of cellulose and simultaneous preparation of multifunctional cellulose materials

Abstract

Green and sustainable cellulose-based materials are of increasing interest to researchers due to the energy crisis and environmental pollution. However, developing green solvents for cellulose is still a big challenge. No longer limited to monoacid-superbase ionic liquids (ILs), this work innovatively proposes novel diacid–superbase ionic liquids that maximally dissolve 15.2 wt% of microcrystalline cellulose (DP = 260) and 9.3 wt% of cotton wool (DP = 685), respectively. The effects of the structure of ILs on cellulose solubility and the interactions between ILs and cellulose during dissolution were analyzed by comparing different types of diacids and superbases. For sustainability, the ILs can be recycled and reused to dissolve cellulose. In addition, the rheological properties of the cellulose solutions were studied for fiber spinning. The cellulose solutions had strong attractive interactions with the substrates and showed universal bonding properties, achieving tensile strengths of 2.39 MPa and 2.28 MPa for wood and bamboo boards, respectively. Through regeneration in a solidification bath and hot pressing, the regenerated cellulose films show structural integrity, dense morphology, a high degree of crystallinity, excellent tensile strength (134 MPa), sufficient thermal stability, and excellent transparency. Finally, the prepared cellulose gel was incorporated into a zinc-ion hybrid supercapacitor (ZHSC) with a wide voltage window, high energy and power density, and excellent cycling performance. In summary, this work presents diacid–superbase ionic liquids for the efficient dissolution of cellulose for the first time. Meanwhile, a variety of high-performance cellulosic materials were prepared, which greatly enrich the possibilities for the use of ILs in the production of functional cellulosic materials.