Synthesis Of Porous Organic Polymers Based Heterogeneous Catalysts For The Catalytic Dehydrogenative Coupling Of Silanes With Alcohols

As an important silicon containing derivative in the organic silicon industry,silyl ethers are commonly used in coatings,rubber,organic/inorganic hybrid material,biomedicine and important hydroxyl protection reagents in organic synthesis.So far,the most economical and environmental method for the preparation of silyl ethers is the dehydrogenative coupling of silanes with alcohols.Homogeneous noble-metal complexs are usually used in this reaction.Although these homogeneous noble-metal complexs exhibit excellent catalytic activity,they are difficult to separate and reuse.Therefore,it is of practical significance to develop a kind of low-cost,recyclable and reusable heterogeneous catalyst for highly efficient catalytic dehydrogenation coupling of silane with alcohol to prepare silyl ethers.In this work,three kinds of metal-based heterogeneous catalysts were designed and synthesized by using porous organic polymers（POPs）with high specific surface area,designable monomers,and controllable structure as supporter or precursors,which were used to catalyze the dehydrogenation coupling reaction of silane with alcohol to prepare silyl ethers.The main results are as follows:（1）Utilizing the electronic interaction of electron-rich group with Pd nanoparticles,Pd nanoparticles supported on basic imidazole functionalized POP were prepared（Pd/PDVB-Vim）.The introduction of the basic site promoted the reaction,and the efficient catalytic dehydrogenation of silane with alcohol was realized under the condition of 30℃,all the 20 mmol dimethylphenylsilane could be converted into the corresponding silane ether in 3 h.Catalyst Pd/PDVB-Vim was also suitable for the dehydrogenative coupling of various silanes with different alcohols.In addition,the electronic interaction of electron-rich groups made Pd nanoparticles stable existence,and the catalytic activity of Pd/PDVB-Vim catalyst did not decrease obviously after 6cycles.（2）Supported Pd nanoparticle catalysts with different hydroxyl content were synthesized from different monomers,and the influence of the surface wettability of the catalysts on the dehydrogenation coupling of silane with alcohol was investigated.The results shown that with the decrease of hydroxyl content,the catalytic activity gradually increased.Including,catalyst Pd/POP-CH₃ prepared with toluene as the monomer shown the optimal catalytic activity,and 5 mmol of dimethylphenylsilane could be completely converted in 8 min at 30℃.However,it took 18 min for the catalyst Pd/POP-OH-1 with phenol as monomer,and 26 min for the catalyst Pd/POP-OH-2 with catechol as monomer.This shown that in the dehydrogenation coupling of silane with alcohol,the hydrophobic and hydrophobic alcohol environment was more conducive to improving the catalytic efficiency of Pd nanoparticles.（3）In order to realized the high efficiency catalytic dehydrogenation coupling of silane with alcohol with non-noble metal based heterogeneous catalysts,nickel sulfide catalysts with uniform support on porous carbon were prepared by pyrolysis of S-POP and Ni salt mixture at high temperature.The catalyst CNS-Ni-600 formed at 600℃shown the best catalytic activity,5 mmol dimethylphenylsilane was converted into the corresponding silyl ether within 30 minutes at 80℃.And catalyst CNS-Ni-600 had well substrate universality and excellent reusability,the catalytic activity did not decrease obviously after 14 repetitions.Combined with the results of various characterization,the excellent performance of catalyst CNS-Ni-600 was due to the defect Ni₃S₂ formed during the reaction.And,the dehydrogenative coupling of silanes with alcohols on nickel-based catalyst was realized for the first time.