Study On Synthesis And Properties Of Metal Organic Framework Based On Triphenylene-2,6,10-Tricarboxylic Acid

In this paper,The triphenylene-2,6,10-tricarboxylic acid(H₃TTCA)is used as the ligand,and the solvothermal synthesis method is used to assemble two three-dimensional metal-organic framework(MOF)with the rare earth metals Ce(?)and Nd(?),[Ce(TTCA)(H₂O)]·DMF·H₂O(Ce-TTCA)and[Nd(TTCA)H₂O]·DMF·H₂O(Nd-TTCA).The composition,structure and stability of Ce-TTCA and Nd-TTCA were characterized by single crystal/powder-X-ray diffraction,elemental analysis,gas adsorption,ultraviolet and thermogravimetric analysis.The photocatalytic hydrogen evolution and CO₂conversion performance of Ce-TTCA and Nd-TTCA were studied,respectively.(1)An exceptionally stable cerium MOF,Ce-TTCA,which was prepared by the solvothermal technology of Ce(NO₃)₃·6H₂O and H₃TTCA.The Ce-TTCA can achieve photocatalytic hydrogen production in both pH=2 and 12 aqueous solutions with Pt as a co-catalyst,with rates of 60.3 and348.8?mol g^-1h^-1,respectively.It is worth noting that the partial oxidation of Ce³⁺in Ce-TTCA to Ce⁴⁺not only enhances the ability to capture light,but also promotes the effective separation of charges,thereby greatly improving the activity of photocatalytic H₂evolution.Among them,the hydrogen production performance of Pt/Ce-TTCA-65 with a Ce⁴⁺content of 65%is 6 times than that of Pt/Ce-TTCA-0,which fully illustrates the key role of the metal oxidation state in the process of photocatalytic water splitting.The experimental and theoretical calculation results further prove that the increase of the metal oxidation state is beneficial to promote the electron-hole separation,thereby improving the performance of photocatalytic hydrogen production.(2)Through solvothermal technology,an ultra-stable three-dimensional metal-organic framework Nd-TTCA constructed by H₃TTCA ligand and Nd(NO₃)₃·6H₂O,which has good thermal stability and chemistry stability.Not only in the air at 300 ^oC for 2 hours but also in boiling aqueous solutions at pH 1-12 for 7 days,its structural framework and crystallinity remained basically unchanged.It is worth noting that Nd-TTCA,which has a strong adsorption of CO₂and has Lewis acidic Nd(?)catalytic sites compared to H₃TTCA.The results of the catalytic conversion of CO₂show that Nd-TTCA is 5 times more active than H₃TTCA in the photocatalytic reduction of CO₂to HCOOH.And the conversion rate of Nd-TTCA in the cycloaddition of CO₂and glycidol to obtain cyclic carbonate is 10 times than that of H₃TTCA.The experimental results further proved that incorporating?-electron-rich organic ligands into Nd-TTCA can greatly improve the catalytic efficiency of the photoreduction of CO₂to HCOOH and the cycloaddition of CO₂and epoxides to obtain cyclic carbonates.