Modulation Of The Pore Environment Of MOFs And Study On Their Adsorption,Catalytic And Molecular Recognition Properties

Metal-organic frameworks（MOFs）are a class of crystalline materials consisting of metal nodes and organic ligands.Due to their flexible composition and structure,MOFs are currently being explored in the fields of adsorption and separation,catalysis,sensing and drug delivery,and are promising new molecular-based materials.Application-oriented molecular design and pore environment regulation is one of the key research topics to advance the development of MOF materials.Methods commonly used for application-oriented tuning include design and functionalization of organic building units,selection of metal nodes,and solvent-induced structure modulation.Important progress has been made in the direction-controlled synthesis of MOF materials,and a series of mature tuning mechanisms have been developed through extensive exploration by researchers.However,the diversity of MOF building units and the expanding range of applications still pose significant challenges in the directed construction of novel functional MOF materials.Further exploration of MOF design and synthesis,as well as enrichment of MOF types and functions,remain highly necessary.This research is centered upon the design of MOFs with pore environments regulated at different hierarchical levels,and the study of their capabilities in gas adsorption,separation,catalysis,and recognition.The primary approach taken involves the synthesis of a series of novel MOF materials through three distinct construction strategies:single-ligand molecule mixed functional group design,mixed dual-ligand solvent induction,and mixed dual-ligand functional group modification.The structures and pore properties of the prepared MOFs were characterized using X-ray diffraction and N₂ adsorption experiments,followed by a systematic investigation of their application performance in CO₂ adsorption and separation,catalytic CO₂ cycloaddition,and DMF/DMA molecular recognition.The main research content is described as follows:（1）An H₂TAIA（5-（4-（triazol-1-yl）phenyl）isophthalic acid）ligand composed of mixed functional groups was designed and assembled with Cu atoms to construct a double-cage MOF（DZU-113）containing unsaturated N sites.The performance of DZU-113 in CO₂ adsorption and catalytic conversion was investigated.Single crystal resolution shows that DZU-113 consists of an octahedral cage with an inner diameter of approximately 0.4 nm and a spindle-shaped nanocage with internal pores of about 0.8 nm x 2.2 nm.Notably,the non-coordinated N atom of the triazole group serves as an open functional site,further enhancing the affinity between the framework and gas molecules.DZU-113 exhibits excellent performance in both CO₂adsorption and catalytic conversion.（2）A mixed ligand consisting of 4,4’,4"-tricarboxytriphenylamine（H₃TCA）and 4,4’-（9,10-anthracenediyl）bis-Pyridine（BPPB）was selected.By controlling the acetonitrile solvent,the metal centers and structures of the MOFs were regulated to construct two examples of two-dimensional MOFs,DZU-115 and DZU-116.DZU-115 with a large number of DMA solvent molecules in the pore channel was able to achieve naked-eye recognition of DMF and DMA solvents with good fluorescence recognition of both solvents compared to the tightly stacked DZU-116.The solid-state fluorescence emission spectra showed that the main peak.（3）Three examples of isomeric microporous column MOFs were synthesized by selecting4,4’,4"-tricarboxytriphenylamine（H₃TCA）as the layer ligand,functionalized pyrazines as the column ligands（PYZ-x,x=-H（DZU-10）,-NH₂（DZU-11）and-OH（DZU-12））and Ni as the metal center.This series of MOFs belongs to a type of bundle-pillar-layer MOF with a Ni6cluster-based node,which is reported for the first time.Their adsorption and separation performance on acetylene and CO₂ were optimized by replacing the modification groups of the column ligands.Based on density functional theory（DFT）,the corresponding adsorption binding sites and binding energies of the gas molecules were revealed,further verifying the experimental results.