Design And Synthesis Of Fluoroanion Microporous Metal-organic Frameworks And Their Gas Adsorption And Separation Performance

Light hydrocarbons（C₁-C₃）,as important raw materials in industrial production,to meet the purity requirements of downstream processing,require separation and purification to achieve fine utilization,and the traditional low-temperature distillation versus solvent extraction method for separating low-carbon hydrocarbon mixtures is often accompanied by a large amount of solvent loss and energy consumption,so it is of great significance to develop new separation techniques for separating low-carbon hydrocarbon mixtures.Metal-organic frameworks（MOFs）are considered to have great potential in gas separation due to their excellent framework diversity and pore channel designability.Fluoroanion MOF materials,as an important branch in MOFs,have good adsorption and separation performance.However,the vast majority of fluoroanion MOFs suffer from the problems of single topology and insufficient species of adsorption sites.In the light of fluoride anionic MOF materials,it is of great interest to develop fluoroanion MOF materials with new structure types with multiple adsorption sites.In this paper,we based on the flexible V-shaped two connected ligands and flexible three connected ligands,several novel structured fluoroanion MOF materials were successfully synthesized,their potential applications in the separation of C₂H₂/CO₂ and C₂H₂/C₂H₄ were explored,and a new strategy for the synthesis of fluoroanion MOF materials was established in situ solvent thermal modulation method,which provided a new idea for the design and synthesis of novel fluoroanion MOF materials.The novel fluorine anion microporous MOF materials SIFSIX-DPA-Cu and TIFSIX-DPA-Cu were synthesized by in situ solvent thermal modulation method,and the structures and properties of the crystals were characterized.The single component gas adsorption test of the two MOF materials was carried out to study their adsorption and separation capacity for C₂H₂/CO₂.The calculation results show that the IAST selectivity of the two MOF materials for C₂H₂ is 6.8 and 6.71,indicating that they have good adsorption and separation performance.The results show that SIFSIX-DPA-Cu can effectively separate C₂H₂ and CO₂ in C₂H₂/CO₂（50/50）multiple penetration experiments simulating actual industrial conditions,and the separation interval is 31min g^-1,which proves that SIFSIX-DPA-Cu has good separation performance and cycle stability.The pillar-cage MOF materials SIFSIX-Cu-TPA,TIFSIX-TPA-Cu,Zr FSIX-TPA-Cu and Nb OFFIVE-TPA-Cu with different fluoroanions were synthesized by in situ solvent thermal modulation method,and their crystal structures and properties were characterized.SCXRD analysis shows that the three MOF materials have large icosahedral cages and small tetrahedral cages with different sizes.In the single component gas adsorption test,the three MOF materials showed high BET surface area(>1200 m² g^-1)as well as high C₂H₂ uptake(>7 mmol g^-1).IAST calculation results shows that the three MOF materials had good separation ability for C₂H₂/CO₂（50/50）and C₂H₂/C₂H₄（1/99）mixture,and achieved a good balance between high adsorption capacity and separation selectivity simultaneously.