Short Channel Design Of Ordered Mesoporous Catalysts And Their Catalytic Of Organic Reaction Medium Water Clean

Mordern chemical industry has resulted in the rapid development of societyand economy. However, it also induces dangerous signal of environment pollutionincluding water, air and soil pollution, noise pollution, radioactive contamination andso on. With the development of chemical industry, the chemical pollution becomesmore and more severe, which has intimidated human health, ecological equilibrium,and sustainable development of social economy. Obviously, the trend of enhancedchemical pollution could not be restrained merely by final cleaning of water, air andsoil., leading to the concep appearance of "green chemistry". Green chemistry isknown as environment-friendly chemistry, whose purpose is to use the chemicalprinciple to prevent environment pollution at the beginning. Using non-toxic andharmless water instead of organic solvents in organic reactions under mild conditions,and non-toxic and harmless supporter to immobilize homogeneous catalysts toaccomplish the reutilization and improve catalytic efficiency are important parts ofgreen chemistry.Heterogeneous catalysts contain the support and active center. Initially, theimmobilized catalysts usually display lower activity and selectivity than thecorresponding homogeneous analogues due to the enhanced steric hindrance, thereduced degree of dispersion, and destroyed chemical microenvironment of activesites. The appearance of periodic mesoporous silic (PMO) brings new vitality. PMOspossess larger surface area and ordered mesopores that can disperse the active centerefficiently and facilitate the diffusion and adsorption of molecules, which greatlyimprove the performance of the catalysts. Our group have done a lot of work aboutfunctional PMOs, and found that compared with heterogeneous catalysts prepared bygrafting method, those by co-condensation have more smooth and unblocked pores,and performs better catalytic properties.In heterogeneous catalytic system, the reactant molecules diffuse to thecatalyst surface first, and then are adsorbed on the active centers to participate in thereaction. After that, the products depart from the catalytic center, and diffuse out of the channel, and finally leave the catalyst. In the whole process, transfer and diffusionof the reactants and product molecules play an important role. The design ofshort-pore ordered mesoporous silica catalysts will promote the diffusion andadsorption of molecules, leading to the improvement of catalytic performance. Basedon this, we mainly focus on design short-channel mesoporous silicas. The detaileddescriptions are listed as follows:1. A novel amine-bridged periodic mesoporous organometalsilica in uniformnanospheres with straight and ordered mesoporous channels was synthesized bysurfactant self-assembly directed co-condensation. The amine-groups integrallyincorporated into the silica walls, leading to high efficiencies in water-mediumKnoevenagel condensation and solvent-free Henry reactions due to the reservation ofchemical environment of active sites and the diminished diffusion limits. Besides thecomparable efficiencies, the present organocatalyst could be easily recycled andreused, showing superiority over the corresponding homogeneous organocatalyst inpractical applications.2. Pd(II) or Rh(I) organometallic catalysts with sphere-like morphologies andwell-ordered two dimensional hexagonal mesoporous channels were synthesized bysurfactant self-assembly directed co-condensation of PdCl2[PPh2(CH2)2Si(OEt3)3]2orRhCl[PPh2(CH2)2Si(OEt3)3]3and TEOS. The catalysts exhibited high catalyticefficiency in water medium C-C coupling reactions, such as Suzuki reaction,Sonogashira reaction and Heck reaction, due to the well dispersion of active sites andshort mesoporous channels which resulted in diminished diffusion limit. Besides, thecatalyst exhibited good stability and could be used repetitively.3. Sulfonic-functional periodic mesoporous organometalsilica was obtained bydirected-sulfonation of ethylene groups of short channels ethylene-bridged periodicmesoporous organometalsilica synthesized by surfactant self-assembly directedcondensation. The ordered mesoporous structure maintained in the result material, andthe sulfonic groups directly attached to the organic framework, leading to unblockedchannels and diminished diffusion limit. It exhibited higher catalytic efficient used inesterification reactions, especially for esterification of long chain carboxylic acids. Based on the characterizations, the correlation of catalytic performance to thestructural characteristics was discussed briefly.