Self-hydrogen supplied reductive catalytic fractionation of lignocellulose over Ru1/Mg(OH)2 for high-yield production of lignin-derived monomers

Ru 1 /Mg(OH) 2 enables hydrogen-free catalytic fractionation of lignocellulose in water. • Single-atom Ru anchored on defect-rich Mg(OH) 2 forms active Ru–O–Mg sites. • C α –OH of β–O–4 linkages acts as an intrinsic hydrogen source for cleavage. • DFT reveals a low-barrier dehydrogenation-assisted β–O–4 scission pathway. • Up to 50.7 wt% aromatic monomers are produced without external hydrogen. Lignin-first biorefining offers a promising route for producing renewable aromatic chemicals; however, most reductive catalytic fractionation (RCF) strategies rely on external hydrogen, limiting their scalability and safety. Here, we report a Ru 1 /Mg(OH) 2 catalyst that enables self‑hydrogen supplied catalytic fractionation (SCF) of lignocellulose in water without external H 2 . The catalyst delivers a remarkably high lignin monomer yield of 50.7 wt% from birch sawdust, approaching the theoretical maximum. Comprehensive characterization (XRD, TEM, XAFS, XPS, Raman, and ESR) reveals that Ru is predominantly atomically dispersed on Mg(OH) 2 and interacts strongly with proton-missing oxygen defects to form unique Ru–O–Mg interfacial sites. These sites generate highly basic oxygen species that promote C α –OH dehydrogenation and subsequently facilitate β–O–4 bond cleavage. Model compound studies confirm that the C α –OH group serves as the intrinsic hydrogen donor, while isotope-labeling experiments and kinetic analysis identify C α –H activation as the rate-determining step. Density functional theory calculations further establish that the dehydrogenation-assisted β–O–4 cleavage pathway has the lowest activation barrier (0.31 eV), validating the endogenous hydrogen mechanism. Collectively, this study provides fundamental insights into hydrogen-free lignin depolymerization and establishes Ru 1 /Mg(OH) 2 as a highly efficient platform for green and scalable lignocellulose valorization. Lignin-first biorefining offers a promising route for producing renewable aromatic chemicals; however, most reductive catalytic fractionation (RCF) strategies rely on external hydrogen, limiting their scalability and safety. Here, we report a Ru 1 /Mg(OH) 2 catalyst that enables self-hydrogen supplied catalytic fractionation (SCF) of lignocellulose in water without external H 2 . The catalyst delivers a remarkably high lignin monomer yield of 50.7 wt% from birch sawdust, approaching the theoretical maximum. Comprehensive characterization (XRD, TEM, XAFS, XPS, Raman, and ESR) reveals that Ru is predominantly atomically dispersed on Mg(OH) 2 and interacts strongly with proton-missing oxygen defects to form unique Ru–O–Mg interfacial sites. These sites generate highly basic oxygen species that promote C α –OH dehydrogenation and subsequently facilitate β–O–4 bond cleavage. Model compound studies confirm that the C α –OH group serves as the intrinsic hydrogen donor, while isotope-labeling experiments and kinetic analysis identify C α –H activation as the rate-determining step. Density functional theory calculations further establish that the dehydrogenation-assisted β–O–4 cleavage pathway has the lowest activation barrier (0.31 eV), validating the endogenous hydrogen mechanism. Collectively, this study provides fundamental insights into hydrogen-free lignin depolymerization and establishes Ru 1 /Mg(OH) 2 as a highly efficient platform for green and scalable lignocellulose valorization. Download: Download high-res image (237KB) Download: Download full-size image