Fuctional Design Of Carbon-Based Catalyst And Its Application In Coupling Reactions

Carbon-based materials have attracted widespread attention in the field of catalysis due to their high surface area and unique physical and chemical properties.In particular,catalysts based on metal nanoparticles/carbon materials have shown extraordinary catalytic activity in organic reactions.The catalytic products prepared by carbon-based materials have been widely used in the fields of pharmacy,biomedicine,agriculture and materials science.Therefore,the demand for carbon-based materials is increasing rapidly,and the development of new synthesis methods and new application areas has become one of the hot topics in chemical science.Carbon nanomaterials,especially heteroatom-doped carbon nanomaterials,are often used in combination with metal particles as a heterogeneous catalyst for organic synthesis.In fact,high surface area,good dispersion,well stability,reusability,and easy recycling are the key reasons for its popularity.In addition,the loading of metal nanoparticles on the carbon support makes it more universal in highly selective catalytic processes.Compared with carbon nanotubes,activated carbon has become the first choice for carbon-based catalysts due to its low cost,large preparation scale,and environmental friendly property.In addition,when carbon-based materials are used as catalytic centers,their higher optical activity is often used to synthesize a variety of organic products in the field of photocatalysis.When carbon-based materials are used as carbon supports,through the process of electron transfer with metal particles,the catalytic activity can be improved and the adsorption of organic substrates can be enhanced.In many organic synthesis reactions,the coupling reaction is of great significance.How to use carbon-based materials to play a catalytic role in the coupling reaction has become a hot topic in the field of catalysis.In this article,the carbon-based catalysts can enhance the catalytic activity of the coupling reactions and improve the catalytic selectivity.The specific research contents are as follows:（1）The shape-selective catalysis of zeolite confined carbon dots in C=N oxidative coupling reactions:Carbon dots are widely used in the field of photocatalysis,and they usually have efficient catalytic activity.Photocatalytic C=N coupling reactions usually bear low selectivity.In order to solve this problem and to improve the conversion,a nano-confined carbon dot catalyst was designed for C=N coupling reaction under visible light irradiation.Using nano hierarchical zeolite silicalite-1 as support,carbon dots were confined in the intracrystalline mesoporous of the zeolite simply and efficiently by in-situ deposition of the template.The shape-selective catalytic property of zeolite material enables the carbon nanodots to only catalyze the substrates that meet the pore size of zeolite framwork.At the same time,the porous structure of the zeolite can enhance the adsorption performance of oxygen molecules and further activation of oxygen.By the synergistic effect of the zeolite support,the confined carbon nanodots have shape-selective catalytic performance,and the catalytic efficiency is much higher than that of the free carbon nanodots.Confined carbon nanodots can also generate confined singlet oxygen active centers,which are universal for C=N oxidative coupling reactions,and can perform shape-selective catalysis on various benzylamine substrates.This research demonstrates the high activity and shape-selective catalytic performance of carbon nanodot catalysts supported by zeolite framwork,and opens new structural design vista for catalysts with carbon materials as active centers.（2）Gold nanoparticle/g-C₃N₄ heterojunction improves the catalytic efficiency of photocatalytic C-C coupling reaction:In the photocatalytic C-C coupling reaction,due to the low activity of metal particles and weak response to visible light,it often fails to meet the needs of C-C bond synthesis.In order to improve the catalytic efficiency,graphitic carbon nitride was designed as support deposited by gold nanoparticles.Due to the response of the graphitic carbon nitride support to visible light,photogenerated electrons and holes are generated under the excitation of visible light,which can activate the substrates of the C-C coupling reaction at both ends respectively,thereby generating the coupling products.The interface effect of heterojunction with gold nanoparticles can effectively accelerate the migration and separation of photogenerated electrons and holes,thus improving the utilization of visible light and the efficiency of catalytic reactions.This research is the formation of C-C bonds under conditions of green chemistry.The high catalytic efficiency of the catalyst under mild conditions and the effective use of excitation light provide an experimental basis for the development of environmentally friendly catalysts in industrial production in the future.（3）Electron-deficient gold/boron doped carbon support promotes activation of substrate at room temperature in C-C coupling reaction:The Stille C-C coupling reaction catalyzed by conventional heterogeneous catalysts usually bear low catalytic activity due to the low atom utilization rate.The reactions always have low conversion and need harsh reaction conditions.In order to solve this problem,a boron-doped carbon support was designed to adjusted the electron density of gold nanoparticle to improve the conversion.Boron-doped carbon support can exist as an electron acceptor on the contact surface with gold nanoparticles due to its electron-deficient properties,thereby generating electron-deficient Au center.The Au nanoparticles with low electron density can automatically activate the C-Br bond in the substrate molecule at room temperature,so that the reaction has catalytic activity that surpass that of homogeneous catalyst and has higher selectivity.In this research,carbon materials exist as support to control the electron density of metal nanoparticles,which not only solves the problem of low catalytic efficiency of gold nanoparticles,but also provides new applications for the electron transfer effect between semiconductors and metal particles.