In this regard, lignocellulosic biomass (LCB) is an attractive alternative due to its abundant availability, carbon neutral nature, and its ability to produce a wide range of fuels and chemicals. [11,12] LCB mainly consists of cellulose (30% to 50%), hemicellulose (20% to 35%), and lignin (15% to 30%), interlinked with each other via a complex bonding network. [13,14] Currently, most of the biorefineries are focusing on the utilization of carbohydrates (cellulose and hemicellulose) for producing bio-ethanol and other chemicals. Moreover, lignin is the major by-product of pulp and paper industry with an annual production of 50 to 70 million tons. [15] However, lignin is mostly burned as a low-value fuel in the industries. [16] Interestingly, it is the only renewable source of aromatic monomers, thus making it a fascinating candidate to produce wide range of aromatics.Lignin is a highly complex 3D heteropolymer, consisting of methoxylated phenylpropanoid units (S unit, G unit, H unit), for providing structural rigidity to the plants. It consists of several COC (α-O-4, β-O-4, 4-O-5) and CC (β-1, β-β, β-5, 5-5) bonds and is interconnected to the cellulose/hemicellulose, thus making its biological or thermochemical conversion challenging (Figure 1a). [11,17] Therefore, the fractionation of LCB via different pretreatment techniques is crucial (Figure 1b). Majority of the pretreatment methods cleave COC (β-O-4) linkages of the native lignin due to their lower (218 to 314 kJ mol −1 ) bond dissociation energy (BDE) while stable CC bonds with higher (384 kJ mol −1 ) BDE are formed due to the recondensation reactions, thus modifying the lignin structure, which is named as technical lignin. [18][19][20] Lower BDE of COC bonds suggests that these bonds are relatively easier to cleave compared to CC bonds. However, depolymerization of native lignin is reported to give monomer yields of approximately seven times that of modified technical lignin. [18] Therefore, the development of new innovative pretreatment strategies that can preserve the β-O-4 linkages of the native lignin is highly desirable. Moreover, it is essential to get an in-depth knowledge of the structural modifications, occurring after the pretreatment, using the different characterization techniques like 1D/2D/3D nuclear magnetic resonance (NMR), 31 P NMR, solid-state NMR,