Preparation And Catalytic Performance Of Nano-Pd Catalysts Supported By Covalent Triazine Frameworks

In today's chemical industry production,most of the chemical reaction processes employ metal oxides as catalysts.However,extremely serious problems such as environmental pollution and energy waste are accompanied.With the advancement of building a green,harmonious and sustainable society,people's desire for a green and pollution-free living environment is becoming more and more urgent.The search for more environmentally friendly and more active catalysts has become the focus in the field of catalysis.Noble metal atoms have a unique electronic structure and usually show more excellent catalytic performance and selectivity than other metals as the active center of a catalyst.However,due to the extremely low content of precious metals on the earth,the loss of precious metal elements during the catalysis process will not only pollute the environment,but also hamper the energy recycling.Recent research has shown that the interaction between the active metal and the catalyst support material benefits the catalytic activity and stability of the catalyst.Taking advantage of the anchoring ability of the nitrogen element in the carrier material,developing catalysts with highly dispersed noble metal nanoparticles on the nitrogen-rich triazine framework materials may be one of the effective ways to address the current energy and environmental problems.In this context,we have prepared a triazine framework material supported nano-palladium catalyst,which show excellent catalytic activity in many types of organic reactions.The research work in this thesis can be divided into the following parts:(1)Select terephthalonitrile and 4,4'-bibenzonitrile with different molecular sizes as the reaction substrates,and carry out the ionothermal trimerization reaction catalyzed by molten Zn Cl₂.By controlling the amount of Zn Cl₂ and the reaction temperature,covalent triazine frameworks with high specific surface area,good chemical stability and rich in nitrogen have been successfully synthesized.(2)The rich nitrogen element in the triazine framework material benefits the uniform dispersion of the palladium nanoparticles on the carrier material,and can also effectively prevent the agglomeration and sintering of the metal nanoparticles.We successfully prepared a series of supported catalysts with ultrafine dispersion of palladium nanoparticles by a simple adsorption-reduction method.Among them,the palladium nanoparticles in the catalyst CTF1-600-Pd show the smallest particle size(?0.7 nm)and the most uniform dispersion.(3)The catalyst CTFs-Pd exhibits excellent catalytic activity and cycle stability in various organic reactions(reduction reactions,coupling reactions,etc.),and shows good generality for all tested substrates.Encouragingly,the catalyst CTF1-600-Pd exhibits better catalytic activity in the tested organic reactions than most of the reported palladium-based catalysts.In conclusion,we have successfully synthesized structure-controllable covalent triazine framework material supported nano-palladium catalysts by controlling the reaction conditions.The catalyst CTFs-Pd catalyzed a variety of organic reactions in a green and pollution-free solvent system and exhibited excellent catalytic performance.Our work expands the application of covalent triazine framework material as a catalyst carrier in the field of heterogeneous catalysis,and provides a new idea for creating a green resource recyclable chemical industry catalysis.