Conversion of lignin to aromatic compounds via C–C/C–O bond cleavage has been an attractive but challenging subject in recent years. We herein report the first protocol that converts lignin models and preoxidized lignin to isoxazole and aromatic nitrile. The isoxazole motif is constructed by condensation of β-hydroxyl ketone with hydroxylamine. Magnesium oxide promotes an oximation reaction and an intramolecular condensation. Aromatic nitriles and esters are obtained via Beckmann rearrangement o

Catalytic valorization of lignin is a sustainable way to provide aromatics for the human society, which depends on the electronic structure of catalytic sites. We herein report the preparation of a carbon-modified nickel catalyst via carbothermal reduction of Ni-doped layered double hydroxides. Lignosulfonate (LS), a lignin resource from the pulp industry, was used as a renewable carbon precursor. The carbon residues in the nickel surface layer changed the 3d electron distribution of nickel, whi

Generation of controllable carbon radical under the assistance of N-oxyl radical is an efficient method for the activation of C–H bonds in hydrocarbons. We herein report that irradiation of α-Fe2O3 and N-hydroxyphthalimide (NHPI) under 455 nm light generates phthalimide-N-oxyl radical (PINO*), which after being formed by oxidation with holes, is confined on α-Fe2O3 surface. The half-life time of the confined radical reaches 22 s as measured by in situ electron paramagnetic resonance (EPR) after

Substituted imidazoles are traditionally synthesized by co-condensation of multiple feedstocks. Herein, we report a new route for the synthesis of substituted imidazoles via photocyclization of readily available amines at room temperature. The reaction is achieved by the visible-light-induced C–C/C–N bond coupling and subsequent dehydrogenation reaction over Mo–ZnIn2S4 as a heterogeneous photocatalyst. A wide range of amines were converted into the corresponding tri- and tetra-substituted imidaz

In many catalytic processes, metastable reaction intermediates are more valuable and desirable than final products. Here, we report Ni–Niδ+ clusters on ceria where the extent of reduction of nickel oxide/ceria in H2 has been optimized. This catalyst shows high selectivity in reducing nitrobenzene to azoxybenzene, the latter usually being metastable. Due to strong electronic metal–support interactions between Ni and ceria, mixed Ni–Niδ+ clusters are formed on ceria even after reduction at 500 °C

Obtaining high selectivity of aromatic monomers from renewable lignin has been extensively pursued but is still unsuccessful, hampered by the need to efficiently cleave C–O/C–C bonds and inhibit lignin proliferation reactions. Herein, we report a transfer hydrogenolysis protocol using a heterogeneous ZnIn2S4 catalyst driven by visible light. In this process, alcoholic groups (CαH–OH) of lignin act as hydrogen donors. Proliferation of phenolic products to dark substances is suppressed under visib

Selective cleavage of C–C bonds is pursued as a useful chemical transformation method in biomass utilization. Herein, we report a hybrid CuOx/ceria/anatase nanotube catalyst in the selective oxidation of C–C bonds under visible light irradiation. Using the lignin β-1 model as a substrate offers 96% yields of benzaldehydes. Characterization results by high angle annular dark field scanning transmission electron microscopy (HAADF-STEM) and energy-dispersive X-ray spectroscopy element (EDX) mapping

This work demonstrates the synthesis of an efficient photocatalyst, Au25(PPh3)10Cl2(SC3H6SiO3)5/TiO2, for selective oxidation of amines to imines. The photocatalyst is prepared via hydrolysis of Au25(PPh3)10Cl2[(SC3H6Si(OC2H5)3]5 nanoclusters in the presence of TiO2 support. The gold nanoclusters exhibit good photocatalytic activity using visible light and under mild thermal conditions for the selective oxidation with molecular oxygen (O2). The turnover frequency (TOF) of 4-methylbenzylamine oxi

For lignin valorization, simultaneously achieving the efficient cleavage of ether bonds and restraining the condensation of the formed fragments represents a challenge thus far. Herein, we report a two-step oxidation–hydrogenation strategy to achieve this goal. In the oxidation step, the O2/NaNO2/DDQ/NHPI system selectively oxidizes CαH–OH to Cα═O within the β-O-4 structure. In the subsequent hydrogenation step, the α-O-4 and the preoxidized β-O-4 structures are further hydrogenated over a NiMo

Selective oxidative cleavage of C-C bond is pivotal for producing functionalized molecules, useful for organic synthesis and biomass utilization. We herein report the oxidative C(OH)-C bond cleavage of secondary alcohols to acids over a copper/1, 10-phenanthroline complex with molecular oxygen as the oxidant. A wide range of secondary alcohols are converted into acids with up to 98% yields. More interestingly, it is effective for breaking up lignin model systems into acids, which is rarely achie