Design And Synthesis Of Heterogeneous Catalyst For Dehydrogenative Coupling Reaction Of Silanes With Alcohols

Silicone ether,as an important organosilicone polymer monomer of silicone rubber,silicone oil,silicone resin and silane coupling agent,has been being widely used in the fields of sealant,adhesive,coating and surface treatment agent.Homogeneous noble metal complex catalysts have been used in the catalytic dehydrogenation coupling synthetic method of silyl ethers.However,these noble metal homogeneous catalysts have many disadvantages such as high cost,complicated synthesis steps,difficult separation of catalysts and ligands from the reaction system,which limit its application in medical,electronic,construction and other fields.Therefore,it is an urgent problem to develop a kind of economical,green,efficient and easily separated heterogeneous catalyst in the synthesis industry of silyl ether.Supported noble metal nanoparticles（NMNPs）heterogeneous catalysts play an important role in the field of catalysis because of their advantages such as simple synthesis,easy separation and recycling.Heteroatom-doped porous carbon materials（HPCMs）are excellent in terms of structure and defect properties,and have the advantages of environmental protection,simple synthesis,metal-free synthesis and large-scale synthesis.Based on the above background,in this paper,porous organic polymers（POPs）and nitrogen and phosphorus co-doped carbon materials have been selected as precursors to synthesize two different types of porous materials to catalyze the dehydrogenation coupling reaction of silanes with alcohols.The synthesis and performance of the above two kinds of heterogeneous porous catalysts have become the core of this paper.The specific research contents are as follows（1）In this study,the porous organic polymers（POPs）was selected as the initial carrier to synthesize platinum supported nanoparticles（Pt NPs）heterogeneous catalyst by ion exchange.The carrier was finely adjusted,the pore size of the carrier was controlled by solvothermal method,and the dispersibility of the catalyst in the system was controlled by surface modification of organic groups.The size and distribution of Pt nanoparticles on the carrier can be adjusted by adjusting the type of porous organic polymer anions（I^-,NTf₂^-）,and the charged stabilizer is essential for controlling the crystal size of platinum nanoparticles.Compared with I^-,NTf₂^-as a charged stabilizer can effectively inhibit the aggregation of ultra-small Pt NPs and avoid the clogging of internal pores.NTf₂^-can replace halide ions（I^-）as a charged stabilizer to stabilize platinum nanoparticles particle.Through a series of characterization and activity tests,the results showd that the platinum particle size of POP-NTf₂@Pt catalyst was about 2.1 nm,and the catalytic activity was high,the silane conversion rate and the silane yield reach 99%,and the cycle times could reach about five times.（2）Using phytic acid as the P-containing monomer and pyrrole as the N-containing monomer to synthesize the N and P co-doped precursor（PA-Py）,and then obtain the N and P co-doped porous carbon material through calcination and pyrolysis,which was used for the dehydrogenation coupling reaction between silane and alcohol.The structure of the catalyst was characterized by a series of characterization methods（TGA,XRD,BET,XPS,Raman,SEM,TEM）.The characterization results showed that the N and P co-doped precursor had a relatively high degree of defects in the structure of carbon materials after calcination at 900℃,and had the highest catalytic activity.The conversion of silane and the yield of silicone ether were up to 99%,and the catalyst could be cycled five times and still had good catalyst activity.We can speculate that the successful doping of N and P heteroatoms and the partial graphitization of the carbon structure work together to change the electronic and geometry structure of the C atoms near the heteroatoms,resulting in high-density defects in the carbon skeleton.Therefore,the catalytically active sites can be successfully introduced,and the strong interaction between the lone pair electrons in the N and P heteroatoms may promote the catalytic performance of the carbon material to a certain extent.