Orbital Coupling Over N-Bridged Zn─Co Atomic Pairs Enables Lignocellulose Valorization.

Production of monophenols and carbohydrates through reductive catalytic fractionation is the key operation for lignocellulose utilization. Metal utilization can be maximized by single-atom catalysts, but catalytic performance is limited by the insufficient activation capability of a single site. Here, N-bridged Zn─Co atomic pairs with compressed Zn─N/Co─N bonds are constructed to enable continuous orbital coupling near the Fermi level, by which the Cβ─O bond of lignin is activated by accepting charge via vacant Co dxz/dyz orbitals and the Cα─OH bond is activated by injecting charge via Zn dxy orbitals. Hydrogen heterolytic dissociation is also facilitated by the compressed Co─N through polarizing H2 to Hδ--Hδ+. Consequently, superior activity is exhibited, by which wood is converted to monophenols with a near-theoretical yield and carbohydrates with 92.2% retention at 200°C, and a TOF of 3.5 h-1 is achieved, 6.1 times that of benchmark 5%Ru/C. A scaled-up operation using the produced phenols as solvent is designed, achieving a high monophenol concentration 85.8 g/L in the resultant liquid and demonstrating excellent industrial potential. A design concept for non-noble-metal catalysts at the atomic orbital level is thus provided for lignocellulose biorefining.