Functionalization Of Metal-organic Frameworks And Their Application In CO₂ Capture And Conversion

With the rapid development of industry,CO₂ emissions have increased year by year,which will constrain the development of economy and society.As a result,it is of great significance to reduce CO₂ emissions.Meanwhile,from another perspective,CO₂ is an abundant,inexpensive,and renewable C1 building block,which has been widely used as an environmentally friendly medium and raw material in the production of fuels,materials and chemical products.Therefore,the development of functional materials that can perform both CO₂ capture and conversion under mild conditions has become a research focus.Functionalized MOFs have the advantages such as high specific surface areas,adjustable structures and modified pore environment,and show attractive application prospect in gas absorption and catalytic conversion.In order to solve the low efficiency of pure MOFs in adsorption and catalysis,the functionalization of MOFs by using mixed ligands or introducing specific functional groups becomes the current research hotspot.In the presentwork,two kinds of functionalized MOFs based nanocomposites were successfully prepared by using a second amino-functional ligand and grinding impregnation.The structures and properties of the nanocomposites were characterized by XRD,N2 adsorption/desorption,SEM,FT-IR,NMR andTGA in detail.The CO₂ adsorption and catalytic performance of the two nanocomposites were then systematically studied.The detailed researches and results are given as follows:（1）Preparation of mixed ligand functionalized ZIF-8 and its application in CO₂ captureFunctionalized ZIF-8 was successfully synthesized via adding an amino-functional ligand during the original synthesis process,and the selective CO₂ adsorption performance as adsorbent was investigated.Since the amino-functional ligand is involved in the framework of ZIF-8,the novel nanocomposites can not only maintain the original thermal stability but also possess more nitrogen-containing sites.It was found that the functionalized ZIF-8 exhibited excellent CO₂ adsorption properties under mild conditions.Under the atmospheric CO₂/N2 atmosphere,the optimum adsorption temperature of functionalized ZIF-8 was 55℃ and the maximum adsorption capacity was 5.83 mmol·g-1.The CO₂ adsorption capacity of the the functionalized ZIF-8 has a significant increase compared with pure ZIF-8 and other known MOFs.（2）Preparation of amino ILs functionalized MIL-101 and its application in CO₂ conversionAmino ILs functionalized MIL-101（Mim-NH₂/MIL-101）was successfully synthesized via grinding-impregnation method to convert CO₂ effectively.The results show that Mim-NH₂/MIL-101 can efficiently catalyze the cycloaddition reaction of CO₂ with epichlorohydrin without solvent under mild conditions.At 0.5MPa,50℃ and 12 h,the conversion of epichlorohydrin and selectivity of chloropropene carbonate are for 96% and 98%,respectively.