Design And Synthesis Of New Mofs Based On Several Examples Of Aryl Carboxylic Acids And Their Selective CO₂/N₂ Adsorption And Separation

The increasing CO₂ emissions that accompany rapidly industrial and economic development are resulting in greenhouse effect and worsening environmental pollution.Therefore,how to reduce the ultrahigh concentration of carbon dioxide has become an urgent and serious issue.metal-organic frameworks?MOFs?have attracted more attention for CO₂ capture in virtue of their superhigh surface area,tunable porosity,rich surface chemical environment and remarkable stability.Five aryl polycarboxylic acid ligands were designed and synthesized,and their structures were characterized by NMR and FTIR in this dissertation,which are 4,4'-?1,5-di-ethoxynaphthalene-2,6-diyl?dibenzoic acid?H₂DCEPN?,4,4'-?1,5-dimethoxy-naphthalene-2,6-diyl?dibenzoic acid?H₂DCMPN?,4,4',4'',4'''-?pyrazine-2,3,5,6-tetrayl?tetrabenzoic acid?H₄TCPP?,5,5',5'',5'''-?pyrazine-2,3,5,6-tetrayl?tetraisophthalic acid?H₈TOCP?and 5,5'-?4,4'-?9-?4-?1-?3,5-dicarboxyphenyl?-1H-1,2,3-triazol-4-yl?phenyl?-9H-carbazole-3,6-diyl?bis?1H-1,2,3-triazole-4,1-diyl??diisophthalic acid?H₆STCP?.The crystal growth conditions of MOFs based on the above ligands were explored,and four new MOFs were synthesized,Co₈?TCPP?₄?BPY?₄·xDMF?BTY=4,4'-bipyridine?,Ni₃?OH?₂?H₂TCPP?₂?BPY?·xDMF,Ni₄?TCPP?₂?BPY?₄?8H₂O and[Ni?DCEPN??BPY??2H₂O]?2DMF.The crystal structure,thermal stability and crystal phase purity of synthesized MOFs were analyzed by TGA,S?P?XRD and FTIR,respectively.The CO₂ and N₂ adsorption selectivities of synthesized MOFs were studied by IAST model.The cyclic regeneration performance of synthetic materials was also judged by calculated heats of adsorption?HOA?.The synthesized Co₈?TCPP?₄?BPY?₄·xDMF has a phase transition in the crystal structure after removing the free solvent molecules with a space group P-1?monoclinic?instead of P2₁/c?triclinic?.The activated Co₈?TCPP?₄?BPY?₄·xDMF has a BET specific surface area of 658.493 m²/g,and the separation factor of this network is 48.35 when the composition ratio of CO₂ to N₂ is 15:85 at 273 K,which can better meet the separation requirements of CO₂.The BET specific surface areas of Ni₃?OH?₂?H₂TCPP?₂?BPY?·xDMF and Ni₄?TCPP?₂?BPY?₄·8H₂O are 152.11 and46.78 m²/g,respectively,but the latter has higher CO₂ selectivity after activation due to its exposed metal sites.[Ni?DCEPN??BPY?·2H₂O]·2DMF has a BET specific surface area of 6.91 m²/g,and can achieve CO₂ separation requirements at 273 and298 K.Four MOFs have moderate HOA values,which are suitable for CO₂adsorption and separation.