## 1 Introduction  
With the depletion of fossil fuels and the rise in global energy demand, renewable energy resources have garnered extensive attention [1]. Under these circumstances, lignocellulosic biomass has emerged as a critical renewable feedstock for synthesizing fuels and chemicals and harnessing energy [2]. Lignocellulosic biomass is composed of three major constituents: cellulose, hemicellulose and lignin. Among these constituents, lignin, a complex and highly branched three-dimensional polymer, is composed of different phenolic units, including guiaacidyl, syringyl, and p-hydroxyphenyl, which are interconnected through C-C and C-O linkages [3]. As a major component of lignocellulosic biomass, lignin accounts for approximately 15-30% of the dry weight of wood and other plant materials. Lignin, alongside cellulose and hemicellulose, holds significant potential as a source of sustainable aromatic compounds [4] and alkane derivatives suitable for liquid fuels [5]. In the context of the biorefinery concept, lignin is a valuable source of aromatics and a key candidate for replacing fossil-based feedstocks in the production of fuels, chemicals, and materials [6]. However, despite its abundance and importance in nature, lignin remains underutilized owing to its unidentified molecular structures, molecular weight fluctuations, complex structure, and robust C-C bonds, which impede efficient conversion processes [7]. To address this, several approaches for lignin depolymerization have been proposed to date, including fast pyrolysis [8], oxidation [9], solvothermal methods [10], and hydrothermal liquefaction [11, 12, 13, 14]. Among these techniques, solvothermal methods have garneredparticular attention for their effectiveness in lignin degradation, utilizing either external hydrogen or hydrogen donor solvents with or without metal catalysts [15]. Both heterogeneous [16] and homogeneous catalysis approaches have been explored for the disruption of lignin's chemical bonds to produce aromatic chemicals [17]. Heterogeneous catalysis typically uses metal catalysts, which can be highly efficient but often involve expensive noble metals such as Pd, Pt, and Ru, or less-efficient metal-based catalysts such as Zn or Cu, which can become saturated with lignin fragments. While homogeneous catalysis overcomes some of these shortcomings, it often requires strong mineral acids or alkaline solutions, posing technical challenges in downstream processing. Hence, green solvents or catalysts are being explored as more sustainable solutions to these environmental and health concerns [18; 19]. In this context, ionic liquids (ILs) are considered a promising class of green solvents [20], particularly for biomass fractionation [21] and lignin depolymerization [22]. Previous studies have demonstrated that acidic ILs can effectively dissolve lignin. For instance, [PERSON] et al. [23] achieved successful lignin depolymerization using 1-H-3-methylimidazol chloride at temperatures ranging from 110 to 150 \({}^{\circ}\)C, which led to the disintegration of alkyl-aryl ether linkages. [PERSON] et al. [24] reported a yield of over 70% in hydrolyzing \(\beta\)-O-4 bonds in lignin model compounds at 150 \({}^{\circ}\)C. However, despite the effectiveness of ILs, their high costs and limited availability have constrained their applications in large-scale lignin depolymerization, prompting the exploration of other green alternatives. Furthermore, given that ILs are entirely composed of ions, their use requires high-purity solvents, which can drastically alter their characteristics owing to ionic or molecular impurities [25]. Recent advancements in deep eutectic solvents (DESs) have considerably improved the efficiency of lignin extraction and biomass fractionation. A deep eutectic solvent is a mixture of two or more compounds that form a eutectic mixture, which exhibits a melting point significantly lower than that of the individual components.