Condensed lignin depolymerization via C–C bond cleavage with a disordered crystalline mesoporous zeolite

The depolymerization of condensed lignin-a byproduct of industrial pulping and biorefining-is crucial for sustainable biorefineries. However, it remains a formidable challenge due to the formation of recalcitrant C-C bonds during lignin isolation, restricting the reactivity and accessibility of the lignin macromolecule. Here, we demonstrate that a disordered crystalline mesoporous zeolite (Meso-Z) synergistically integrates strong acidity with enhanced mass transfer efficiency to process this bulk feedstock. Compared to conventional microporous zeolite, Meso-Z achieves 3.7-7.9 times higher yields (32.0-45.6 wt%) of aromatic monomers and dimers (MDs) from condensed lignin oligomers by C-C bond cleavage, thus enabling the total yields to exceed the theoretical maximum defined by C-O bond cleavage by 250-759%. Mechanistic studies reveal that this exceptional performance arises from Brønsted and Lewis acid-assisted hydrolysis and hydrogenolysis of C_α-C_aryl bonds, facilitated by the zeolite's mesoporosity. Meso-Z also shows robust recyclability, maintaining stable catalytic activity over ten consecutive cycles. This work provides an efficient strategy for depolymerizing condensed lignin, paving the way for the valorization of industrial lignin streams.