The Mesoporous Metal / Oxide Catalyst Is Used For The (α) C-H Bond Activation Reaction

The activation of inert C-H bond is one of the most rapidly developing directions in the field of chemistry in recent years. High added organic compounds can be synthesized by inert chemical bond activation from simple organic compounds, which can greatly improve the synthesis efficiency and atomic economy. However, the traditional homogeneous C-H bond activation reaction facing some problems, such as the catalyst is difficult to be recycled, requires complicated and expensive ligands, the reaction condition is harsh（anhydrous and anaerobic）, using additives, dependent toxic flammable organic solvents and heavy metal residues and other issues. The heterogeneous catalyst has natural advantages in this area, which can provide reference for potential industrial application. From the point of view of green chemistry, we have synthesized functionalized mesoporous metal/oxide catalysts for the coordination environment of metal/oxide and the chemical properties of the surface, which can achieve the purpose of activating the inert（α-） C-H bond. In this paper,we have studied the palladium-catalyzed indole C2 selective arylation reaction in aqueous medium, as well as CeO₂-C catalytic oxidation of benzyl alcohol under alkali system for the elimination mechanism benzaldehyde process α-C-H bond. And we have got the following interesting results:（1） A phase-transfer-agent-functionalized ordered mesoporous resin material, which is synthesized by a micelle-templated approach, is used to support a heterogeneous Pd catalyst. The catalyst possesses an interpenetrated inorganic-organic framework. Coordination with highly dispersed Pd nanoparticles creates an electronically rich environment for surface atoms and causes a distinct enhancement in the stabilization and accessibility of these particles to organic substances in aqueous solution.The ligand-free mesoporous Pd catalysts are active in the C-2 arylation of N-methylindole with diphenyliodonium salt to yield N-methyl-2-phenylindoleusing water as a solvent without any other additive or exclusion of air. The catalysis likely occurs on the Pd surface rather than in solution, as evidenced by a negligible reduction in activity upon the addition of mercapto-functionalized mesoporous silica（SH-Silica） poison but a significant quenching of catalysis by the separation of solids by hot infiltration. The heterogeneous mesoporous polymer-based Pd catalysts are stable, exhibit undetected metal leaching, and can be re-used more than eight times. The yield of target product over Pd/SBA-15, Pd/pristine MP, commercial Pd/C and Pd/FDU-15 are lower than those on Pd/11.5ODDMA-MP, thus highlighting the important role of the integrated phase transfer agent on the pore wall when coordinated with Pd.（2） Based on lyotropic liquid crystal template technique, we have synthesised the mesoporous CeO₂-C catalyst. CeO₂-SiO₂, polycrystalline CeO₂ nanoparticles, CeO₂-C-RC and CeO₂-SiO₂-RS catalysts were synthesized according to other synthesis methods. These catalysts were used in the oxidation of benzyl alcohol to benzene formaldehyde under base-free condition in air. The activity for the oxidation of benzyl alcohol follow the order of 30% CeO₂-C >> CeO₂-SiO₂-RS = CeO₂ > CeO₂-C-RC ≈ 30% CeO₂-SiO₂. Furhermore, 30% CeO₂-C catalyst to benzaldehyde yield of 80%, which is 20 times polycrystalline CeO₂ activity and selectivity of up to 99%. CO₂-TPD, O₂-TPD, XPS and Raman spectroscopic characterization results revealed that, 30% CeO₂-C catalyst has the highest concentration of oxygen defects as well as surface reactive oxygen species. The possible mechanism is that, 30% CeO₂-C catalyst for high oxygen defect concentration in the molecular oxygen to produce activated species peroxy O-, and the O- species can be reproduced and converted to active species superoxide O₂-, which further to promote the oxidation of benzyl alcohol elimination of the α-C-H bond.