The Study Of Synthesis And Gas Adsorption Properties Of Metal-organic Framework Based On Triazolyl-carboxylate Ligands

Metal-organic frameworks（MOFs）have attracted the attention of many researchers due to their large specific surface area and designability,showing excellent performance in various fields.More and more types of MOFs are synthesized.For example,through anion regulation,MOFs with different coordination modes between the same ligand and metal ions can be obtained.Polyporous MOFs show excellent performance in gas adsorption and separation,and can solve the shortcomings of traditional separation methods such as high energy consumption,complex operation and low selectivity.Therefore,MOFs show huge application potential in gas storage and separation.In this paper,we synthesized some polyporous MOFs by anion regulation,and explored the properties of materials in adsorption and separation.The specific work is as follows:In the first chapter,the concept and characteristics of MOFs are summarized,and briefly describes the research status of MOFs in light hydrocarbon and other adsorption and separation fields,and the research significance and progress of this paper are presented.In the second chapter,a series of polyporous MOFs were synthesized and their adsorption and separation properties were studied.In previous work,we designed and synthesized an organic ligand 3-hydroxy-4-（4H-1,2,4-triazole-4-yl）benzoic acid（HL）containing triazole and carboxyl bifunctional groups,and synthesized two polyporous complexes（Ni-MOF 1,Co-MOF 2）.At the same time,we also designed and synthesized 2-methyl-4-（4H-1,2,4-triazole-4-yl）benzoic acid（HL1）and3-methyl-4-（4H-1,2,4-triazole-4-yl）benzoic acid（HL2）with different substituents.Three MOFs（Ni-MOF 3,Ni-MOF 4,Co-MOF 5）,which are isomorphic to Ni-MOF1,were synthesized with these two ligands.All the five MOFs have high porosity micropore structure.It is worth noting that Ni-MOF 1,Ni-MOF 3 and Ni-MOF 4 have good water stability,and the adsorption capacity of C₂H₆,C₃H₈,C₂H₂ and C₂H₄ is higher than that of CH₄.The adsorption heat curves of Ni-MOF 1,Ni-MOF 3 and Ni-MOF 4 have obvious differences,indicating that the difference of substituents leads to the difference of the force between adsorbent and adsorbent.It is obvious that the C₂H₂ adsorption heat of Ni-MOF 1 is only 28.0 k J mmol^-1,and that of Ni-MOF 3and Ni-MOF 4 is 40.2/42.2 k J mmol^-1.The adsorption heat of C₂H₄ of Ni-MOF 1 and Ni-MOF 4 is 38.0/37.9 k J mmol^-1,while that of Ni-MOF 3 is only 27.2 k J mmol^-1.At298 K,the adsorption capacity of Ni-MOF 1 for C₃H₈ was 79.8 cm³ g^-1.Importantly,at 0.03 bar,the adsorption capacity of C₃H₈ was 50.5 cm³ g^-1,accounting for 63.3%of the total adsorption capacity.At 0.05 bar,the adsorption capacity of C₃H₈ was 74.3%of the final adsorption capacity.Ni-MOF 1,Co-MOF 2,Ni-MOF 3,Ni-MOF 4 and Co-MOF 5 all showed that the adsorption capacity of C₃H₈ increased rapidly in the low pressure area.The simulation of natural gas components was conducted to test the breakthrough of CH₄/C₂H₆/C₃H₈（85:10:5）on Ni-MOF 1 and Ni-MOF 3 separation columns at 298 K.The results showed that Ni-MOF 1 and Ni-MOF 3 could completely separate CH₄/C₂H₆/C₃H₈.In addition,in order to understand the adsorption mechanism,the adsorption sites of Ni-MOF 1 were simulated by GCMC technique.In the third chapter,through anion regulation,we synthesized two kinds of sulfate coordination MOFs（Co-MOF 6,Co-MOF 7）by reacting with L2 and Co（Ⅱ）.Four different anionic coordination or free MOFs（Cu-MOF 8,Cu-MOF 9,Cu-MOF10,Cu-MOF 11）were synthesized by the reaction of L2 with Cu（Ⅱ）and the addition of different anions(NO₃^-,PO₄^2-,Cl^-,etc.).The structure of MOFs was determined and analyzed by X-ray single crystal diffraction,and the thermal stability of MOFs was characterized.The adsorption and separation properties of C₂H₂/CO₂/CH₄ for Co-MOF 6 and Cu-MOF 10 were tested.The IAST selectivity of C₂H₂/CO₂ for Cu-MOF 10 reached 7.0 at 298 K and 1 bar.Co-MOF 6 has a moderate adsorption heat of C₂H₂/CO₂/CH₄,and the breakthrough experiments show that Co-MOF 6 can achieve complete separation of binary components C₂H₂/CO₂,C₂H₂/CH₄,CO₂/CH₄（50:50,v/v）and ternary components C₂H₂/CO₂/CH₄（1:1:1,v/v/v）.