Synthesis,CO₂ Gas Capture And Catalytic Conversion Properties Of Several Amide/Amino Modified MOFs

MOFs are one of the porous crystalline materials with the largest internal pore volume,the largest specific surface area,and the smallest skeletal density,with good crystallinity and high porosity.Their structures can often be deduced from the directionality of the organic linkers and the coordination geometry of the metal building blocks.From this point of view,metal-organic frameworks can be synthesized largely by designing the desired structure and pore size.The pores of MOFs contain polar groups and numerous nucleophilic sites,so it can be used for carbon dioxide capture and catalytic conversion to alleviate the problem of excessive carbon dioxide emissions and facilitate the production of fine chemicals required by industry.In this paper,three MOFs containing different functional groups were prepared,and their synthesis methods,crystal structures,stability,and catalytic conversion performance were deeply explored.The main research results are as follows:1.Synthesis of organic ligands and metal-organic frameworksThree novel organic ligands with different functional groups were synthesized by acyl chloride reaction and coupling reaction,respectively,H₄L₁（5-（（2,5-bis（methoxycarb onyl）phenyl）carbamoyl）mphthalicacid）,H₄L₂（2,2’-（oxalylbis（azadiyl））diterephthalic acid）and H₂ABP（5-（4-amino-5-bromopyridin-3-yl）mphthalic acid）.According to crystal engineering,three different new MOFs crystal materials were synthesized by thecoordination of metal divalent copper ion and the above organic ligands under suitable conditions,which were named HNUST-14,HNUST-15 and HNUST-16,respectively.By means of characterization methods such as PXRD、FTIR、TGA,the results show that the three MOFs are highly stable in nature and structure,which lays a foundation for exploring the catalytic conversion performance of MOFs for CO_2.2.Research on CO₂ capture performance of metal organic framework materialsBenefiting from its open metal sites,extremely small and amino-functionalized channels,HNUST-16 shows high carbon dioxide capture（5.425 mmol/g at 1 k Pa and273 K,and 3.1925 mmol/g at 1 k Pa and 298 K）.As well as good selectivity for carbon dioxide to N₂（35.27 at 273K,25.16 at 298K）,carbon dioxide also has good selectivity for CH₄（5.89 at 273K,2.06 at 298K）.At 77K,the adsorption of N₂ by HNUST-16 exhibited a reversible microporous type I adsorption isotherm.The BET and Langmuir surface areas were 1516.1 m²/g and 1490.1 m²/g,respectively,and the total pore volume of single-point adsorption was 0.6361 m³/g.The adsorption curves of CO₂,CH₄ and N₂ of HNUST-16 were detected under low pressure and high pressure conditions,respectively.The results show that the material has high CO₂adsorption capacity,and the CO₂ and CH₄ adsorption enthalpy and CO₂/N₂ ofHNUST-16 were calculated.,CO₂/CH₄ gas adsorption selectivity,which proves that HNUST-16 has good gas selection and separation ability.3.Research on the catalytic conversion performance of metal organic framework materials for CO₂Based on the example of HNUST-16 catalyzing the reaction of CO₂ and epoxy compounds to synthesize cyclic carbonate,we have studied its catalytic performance.According to the results of the five-round catalytic conversion of ¹HNMR,when epichlorohydrin,cyclic When oxybromopropane is used as the substrate,the catalytic conversion effect is the best,and the material still has good catalytic performance after repeated catalysis,which provides the possibility for the recycling of the catalyst.