Performance Of BTC-based Catalysts In Synthesis Of Cyclic Carbonates From CO₂

Human activities lead to an increase in carbon dioxide concentration in the atmosphere as an important cause of climate warming.Designing scientific methods to convert carbon dioxide into some value-added product can be used as a promising strategy to reduce carbon dioxide emissions.As a precious C1 resource,carbon dioxide is rich,cheap and non-flammable.Carbon dioxide has received widespread attention for developing various valuable strategy to reduce CO₂ emissions in line with the requirements of green chemistry,with greater environmental and economic effects.For CO₂ conversion under mild conditions has made it still a very attractive and significant challenge.The use of carbon dioxide and epoxides to form cyclic carbonates is considered to be the most environmental friendly way of chemically fixing carbon dioxide,the utilization of the atoms is 100%.Cyclic carbonates are important compounds with a wide range of applications.It is widely used in polar aprotic solvents,lithium-ion battery electrolytes,synthesis of monomeric polymers,degreasing agents,petroleum additives and cosmetics.However,the main drawback is the chemical inertness of carbon dioxide,which has excellent stability in terms of thermodynamics and kinetics.It is necessary to overcome the chemical inertness of CO₂ molecules for its activation and rational use,and the use of catalysts is necessary.This paper discusses the application of three different BTC-based catalysts in the reaction of carbon dioxide and epoxides to synthesize cyclic carbonates.The catalytic performance and stability of the catalysts prepared using carbon dioxide to synthesize cyclic carbonates are systematically studied and further developed.The use of catalysts in different epoxides provides a valuable reference for the development of highly efficient and stable chemically immobilized carbon dioxide catalysts.The specific work is as follows:1.Three-dimensional structure of Zn-BTC was synthesized by solvothermal method.The binary catalytic system of Zn-BTC combined with n-Bu₄NBr shows a high catalytic activity in the cycloaddition reaction of carbon dioxide and epoxide.[Zn₃?BTC?₂]unit has Lewis acid and base catalytic sites with strong nucleophilic anionic promoter?TBAB?to play its good synergistic effect.Each reaction condition was optimized,and the yield of cyclic carbonate was as high as 99%under relatively mild and zero solvent addition reaction conditions.We have also applied Zn-BTC catalysts to other epoxides and found that they also have highly efficient catalytic properties.Therefore,we have also proved the universality and efficiency of Zn-BTC catalysts in the cycloaddition reaction between epoxides and carbon dioxide.As a heterogeneous catalyst,Zn-BTC can be easily separated and reused many times,and the catalytic activity and the structure of the catalyst itself will not change significantly,showing a unique chemical stability and thermal stability.2.The Co-BTC coordination polymer was synthesized by solvothermal method and it was proved that it has a highly efficient catalytic effect on the cycloaddition reaction of carbon dioxide and epoxide.In the presence of the co-catalyst tetrabutylammonium bromide,the optimized reaction conditions were determined,and then the catalytic mechanism of the Co-BTC/TBAB catalytic system was investigated,it was confirming the presence of medium-strength acid and basic sites present in the Co-BTC promoted the reaction.The application of Co-BTC catalyst to other epoxides also has high catalytic performance,which also indicates that The general application of Co-BTC catalysts in the cycloaddition synthesis of cyclic carbonates is also illustrated.The catalyst has no significant loss of activity after multiple recycling.Through various characterization methods,it can be seen that there is no obvious change in the structure of the catalyst after recycling,further illustrating the stability of the Co-BTC catalyst.3.Five kinds of Ni-Co-BTC bimetallic catalysts with different Ni/Co molar ratios were synthesized and used in the reaction of carbon dioxide and epoxide to synthesize cyclic carbonates.The catalysts with the different molar ratio of Ni/Co of0.1,0.3,0.5,0.8,and 1 have a certain regularity in morphology.By testing the catalytic performance of different Ni/Co molar ratio catalysts,it was found that the Ni/Co-BTC-0.8 catalyst with Ni/Co ratio of 0.8 had the best catalytic performance combined with tetrabutylammonium bromide under relatively mild reaction conditions.Various reaction parameters were selected and optimized to determine the optimal reaction conditions.The application of Ni-Co-BTC-0.8 catalyst to other epoxides,the same high-efficiency catalytic performance also confirmed the universal application of Ni-Co-BTC catalyst in the cycloaddition reaction of epoxide and carbon dioxide.Through various characterization methods,it can be seen that there is no obvious change in the properties of the catalyst after recycling,further illustrating the stability of the Ni-Co-BTC catalyst.In terms of catalytic mechanism,the Ni-Co-BTC catalyst contains moderately acidic sites and basic sites.After the catalyst is recycled,it still maintains a strong Lewis acidic and basic sites,which may also be the reason why it still retains high catalytic activity.