The Structure And Action Site Design Of Novel Functional Porous Materials And Their Properties

Recently,metal-organic framework（MOF）and porous organic framework（POF）have attracted extensive attention due to theirs designable structure and function,high porosity,large surface area,etc.Since the pore structure and action site have great influence on the adsorption process and catalytic activity of the material,how to design the structure and action site of materials is the key to prepare adsorbents and catalysts with high performance.Based on the intrinsic advantages,we designed and synthesized a series of MOF and POF materials for the industial gases separation and photocatalytic systems.The major work is as follows:（1）A synergistic CO₂ enhancement mechnism with dual-Li⁺sites was proposed,which greatly improves the CO₂affinity of MOF,achieving the ultahigh CO₂adsorption separation selectivity.By the introduction of polyacrylic acid（PAA）with abundant flexible carboxyl sites into the framework of Ui O-66,the synergistic dual-Li⁺sites in MOF were realized by construction of Li⁺@PAA@Ui O-66composites.Notably,the as-synthesized 0.1 M Li⁺@PAA@Ui O-66 composites exhibit steep adsorption isotherms under the low pressure region,which has never been observed in any other Li-doped adsorbents.Meanwhile,it shows the ultrahigh separation selectivity of CO₂/N₂ and CO₂/CH₄（6341 and 1904）in the finite dilution condition,surpassing all of reported Li-doped adsorbents.In addition,DFT calculations indicate that the more stronger interaction between dual-Li⁺site and CO₂ can be achived compared with the situation of single Li⁺site;（2）A similar straegy of the introduction of dual-Na⁺sites into POF material to enhance the CO₂ separation was proposed.The POF-1 with abundant and adjacent phenolic hydroxyl sites was prepared firstly.The POF-1-2.5 M Na material was obtained by the introduction of low-cost Na site into the POF-1.Therefore,the synergistic dual-Li sites strategy was extended to the lower cost Na system.Due to the existence of dual-Na sites,POF-1-2.5 M Na shows sharp adsorption isotherms in the low pressure region,and CO₂/N₂ and CO₂/CH₄ separation selectivity（220.7 and55.3）of this material is 10 times higher than that of POF-1,achieving excellent separation efficiency;（3）An idea of utilizing the zwitterionic MOF（zw-MOF）to improve the dispersion of ionic liquid（IL）in the pore channel of MOF was proposed.The gas separation performance of as synthsized IL@zw-MOF composites was boosted enormously.The Ui O-66-SO₃^--NH₃⁺zw-MOF containing both negative and positive charge group was prepared,and Ui O-66-SO₃^--NH₃⁺@IL composites were obtained by impregnation method to introduce the IL.Due to the electronic interaction between the positive and negative charges in zw-MOF and those in IL,highly dispersion of IL in MOF can be realized,thus that active sites of IL were full exposed as much as possible,which makes the Ui O-66-SO₃^--NH₃⁺@IL composites show excellent separation selectivity,and its CO₂/N₂ and CO₂/CH₄ separation selectivity（108.7 and 19.0）is 1-2 orders of magnitude higher than that of single ionic MOF@IL;（4）CTF material with tricarbazole structure unit was synthesized,and the ultramicropore structure was introduced into CTF-DCTC by changing the synthesis conditions.It was found that the ultramicropore structure in CTF-DCTC is conductive to ethane/ethylene（C₂H₆/C₂H₄）separation with preferential adsorption of C₂H₆.The ultramicropore of carbazole-based CTF-DCTC was controlled through changing the preparation temperature,and CTF-DCTC-500 with ultramicropore and CTF-DCTC-400 without ultramicropore structure were obtained.Compared with CTF-DCTC-400,the introduction of ultramicropore into CTF-DCTC-500 not only improves the adsorption uptake of C₂H₆,but also exhibits distinct C₂H₆/C₂H₄separation behavior,which is the first reported CTF material with preferential adsorption of C₂H₆.Notably,the separation selectivity of this material for C₂H₆/C₂H₄ at 1 bar is up to 2.08,which is higher than that of reported COF materials.Furthermore,CTF-DCTC-500 also possesses the high chemical stability and favorable recycling stability;（5）The propionic acid（PA）etching method was utilized to realize the simultaneously construction of oxygen vacancy and hierachical pore structure of MIL-125-NH₂,which can greatly facilitate the adsorption and photocatalytic degradationof organic pollutant.The oxygen vacancy and hierarchical pore structure of as-synthesized H-MIL-125-NH₂-V_O material were characterized by the electron spin resonance（ESR）and N₂ adsorption-desorption isotherms.The result shows that the exsitence of hierachically porous structure improves the adsorption of Rh B,shortens the distance between free radical and substrate thus enhancing the effective availability of free radicals,and increases productivity of free radicals owing to the rich oxygen vacancy.Under the combined contribution of oxygen vacancy and hierarchical pore structure,H-MIL-125-NH₂-V_O not only exhibits the large adsorption amount for Rh B,but also shows high photocatalytic activity.The removal effeciency of this material for Rh B can reach 99%,and the catalytic rate constant is about 8 times that of pristine MIL-125-NH₂.This work hightlights the important contribution of hierarchically porous and oxygen vacancy for adsorption and photocatalytic performance of MOFs.