Preparation Of Porous HOFs And Their Gas Adsorption And Separation Properties

Hydrogen-bonded Organic Frameworks（HOFs）are emerging porous crystalline materials composed of supramolecular synthons linked together by hydrogen bonds,which possess high structural crystallinity,strong solution process-ability,easy purification,and self-healing property.Therefore,they have received extensive attention and research in various applications such as gas adsorption and separation,proton conduction,fluorescence,and sensing.However,the weak hydrogen bonding forces make it difficult to obtain stable HOFs with permanent porosity,which greatly limits their development.In this study,two different carboxylic acid-based organic ligands were used,and two HOFs with permanent porosity were synthesized using solvothermal synthesis method,and their structures were characterized.The application of gas adsorption and separation was also studied.The main research contents are as follows:（1）A novel HOF material,HIAM-102,was synthesized by using an organic ligand H₃TBTC with C₃ symmetry through a solvent thermal method in acetic acid solution.The structure of the material was determined and characterized by SC-XRD,PXRD,TGA,and other methods.The results show that the synthesized HIAM-102 has a hbc topology structure and a stable one-dimensional pore channel.The specific surface area and pore volume of this material are 191.05 m²·g^-1 and 0.10 cm³·g^-1,respectively.In addition,the material exhibits excellent thermal stability,chemical stability,and water stability.Single-component gas adsorption tests show that at 278 K and 1 bar,this material has a preferential adsorption capacity for C₂H₆ in the low-pressure region and a high C₂H₆/C₂H₄ selectivity.Through penetration testing,the separation performance of HIAM-102 for C₂H₆/C₂H₄（50/50;10/90;v/v）mixed gas is further tested in dry and humid environments.The test results show that this material does not change significantly in both environments and is not affected by the moisture content in the feed gas,making it the first HOF material that achieves C₂H₆/C₂H₄ separation in such a humid environment.（2）Increasing the number of hydrogen bonds in the structure of HOFs and introducing appropriate intercalation can improve their stability.Therefore,a new HOF material HIAM-103 with permanent porosity was synthesized using a flexible organic ligand H₆PET containing six carboxylic acid groups as a precursor via a thermal synthesis method.The material was comprehensively characterized by SC-XRD,PXRD,BET,TGA,etc.The results showed that HIAM-103 had a six-fold intercalated acs topology,which resulted in very good thermal and water stability.The specific surface area of HIAM-103 was 1085 m²·g^-1,and the pore volume was 0.42 cm³·g^-1.Single-component gas adsorption tests showed that HIAM-103 had the ability to purify CH₄ from six components,including CH₄,C₂H₂,C₂H₄,C₂H₆,C₃H₆,and C₃H₈.The calculated IAST adsorption selectivities of HIAM-103 for CH₄/C₂H₂（50/50;v/v）,CH₄/C₂H₄（50/50;v/v）,CH₄/C₂H₆（50/50;v/v）,CH₄/C₃H₆（50/50;v/v）,and CH₄/C₃H₈（50/50;v/v）at 298 K and 1 bar were 10.4,8.9,8.9,150.7,and 150.7,respectively.The calculation of adsorption heat verified that HIAM-103 had weaker interactions with CH₄.Finally,penetration tests further verified the excellent performance of HIAM-103crystal material in purifying CH₄.