Assembly Of Highly Stable Porous MOFs And Their Properties Of Adsorption And Separation And Luminescent Detection

As a new kind of inorganic-organic hybrid porous materials,metal-organic frameworks?MOFs?combining the activity of metal ions with the tunability and functionalization of organic ligands,has been favored by researchers in the fields of gas separation,fluorescence detection and heavy metal ions capture.Over the past 20years,the development of MOFs materials has gone through an exploratory process from structural design,synthesis to property application.With the efforts of numerous researchers,MOFs materials are developing towards the goal of practical application.However,the most fatal disadvantage of MOFs materials is the structural instability,which is like a gap blocking the road to practical application of MOFs materials.Currently,stable MOFs materials have been reported in two categories:One kind is polynuclear MOFs materials constructed with carboxylate-based ligands and high-valent metal ions,such as Zr-MOFs and Al-MOFs;The other kind of MOFs materials is constructed with azolate ligands and divalent metal ions,such as ZIFs and MAFs materials.In addition,there are few stable MOFs materials constructed by N and O mixed coordination groups,and relatively few reports on such materials are reported.This thesis mainly focuses on the construction of stable MOFs materials by N and O hybrid ligands and mixed ligands of N and O,as well as the research of those materials in gas adsorption and separation,lead capture and detection.The main contents include the following three aspects:?1?We choose the nitrogen ligand benzotriazole?Hbtz?and 1,2,3-triazole?Hvtz?purposefully to construct the stable[Zn₉]and[Zn₅]SBUs.Under the synergistic coordination of carboxylate-based ligands and those SBUs,four stable MOFs materials were synthesized successfully,[Zn₉?btz?₁₂?atdbc?₃?DMF?]·3DMF·12H₂O?compound1?,[Zn₄?btz?₆?bcpt?]·3DMF?compound2?,[Zn₁₀?vtz?₁₂?TPTA?₂?DMA?₂]·2DMA·4H₂O?compound3?and[Zn₁₀?vtz?₁₂?TADIPA?₂?DMF?₄]·DMF·6H₂O?compound 4?.Compounds 1 and 2 are polynuclear zinc structures constructed by benzotriazole,which have the interpenetrated structures and are highly stable to acid and base solutions.In the CO₂ and N₂ adsorption process,compound 1 displays breathing behavior characteristic of the flexible framework.Due to the influence of structural interpenetration,there exists an ultramicropore with the diameter of 3.4?in the structure of compound 2.The ideal pore size enables compound 2 to adsorb O₂,but not N₂ at all,thus achieving a perfect separation of O₂/N₂.Compounds 3 and 4 based on[Zn₅?vtz?₆]metal clusters are interpenetrated MOFs structures,and both exhibit stability under acid and base solutions.There exist multiple and narrow channels in the structure,which make the framework have a strong affinity with C₃H₈ molecules.Compounds 3 and 4 exhibit excellent selective separation for C₃H₈/CH₄.Compared with compound 4,the functionalized compound 3 can absorb more CO₂ and C₂H₂,and displays higher selective separation for CO₂/CH₄ and C₂H₂/CH₄.?2?Using appropriate metal centers and amino functionalized carboxylate-based ligands,four anionic/amino functionalized MOFs materials were successfully synthesized,[Mn?bdfdpa??H₂O?₂]·2[?CH₃?₂NH₂]?compound5?,[Zn₆?tpta?₂?ad?₄]·6DMF?compound 6?,[Zn₄?atdbc?₂?tz?₄]·5DMF·EtOH?compound 7?and[Zn₈?ad?₄?atdbc?₆O]·2[?CH₃?₂NH₂]·9DMF·5H₂O?compound 8?.The structure of compound 5 contains a large number of dimethylamine cations that balance the charge of framework.During the Pb²⁺ion adsorption process,compound 5 can effectively remove Pb²⁺ions from the solution by ions exchange.The?-?interaction between the ligands greatly enhance the stability of the framework,and compound 5 exhibits fluorescence detection of Pb²⁺ions.Four-coordinated zinc bonding together with 1,2,4-triazole readily form?3,3?connected layered structures,and the layers are connected with each other by the support of carboxylate-based ligands to construct the amino functionalized compound 7.The functionalized compound 7 can not only selectively adsorb and detect Pb²⁺ions in water,but also has good reusability and structural stability,so that compound 7 can be used as a dual-function material to adsorb and detect Pb²⁺ions in environmental pollution.Compounds 6 and 8 are polynuclear stable MOFs materials constructed from adenine.Compound 8 not only has anion framework,but also has a large number of amino groups and the high specific surface area,which makes it exhibits superhigh adsorption capacity of Pb²⁺ions and excellent selective separation for C₃H₈/CH₄.?3?Using the N and O hybrid ligands,three isostructural stable MOFs materials were constructed successfully,[Cu₄?L₁?₄?OH??NO₃?]·2?NO₃?·4DMF?compound 9?,[Ni₄?L₁?₄?OH??NO₃?₃?DMF?₂]·3DMF·4H₂O?compound10??[Ni₄?L₂?₄?OH??NO₃?₃?DMF?₂]·3DMF?compound 11?.Compounds 9,10,and 11 have excellent thermal stability,chemical stability and C₃H₈/CH₄ selective separation.Although the three compounds have isostructural structures,there is a slight difference in the coordination models of the metal centers.Due to Jahn-Teller effect,Cu in the structure of compound 9 adopts five coordination with a square pyramid configuration.Compared with the saturated coordination of metal center in compounds 10 and 11,compound 9 has more open metal sites and shows higher CO₂ adsorption capacity.However,compounds 10 and 11 exhibit higher stability.