Syntheses,Structures And Properties Of Lanthanide-Doped Titanium Oxo-Clusters

Photoinduced water splitting is regarded as one of the most promising energy sources forthe preparation of hydrogen.Titanium oxo-clusters(TOCs),as the earliest known model water oxidation catalysts(WOCs)of TiO2,offer an opportunity to understand the relationship between structure and chemical reactivity.Because the band gap of the TOCs is often close to or even larger than that of anatase,various metal ions are introduced into the TOCs to reduce their band gaps.Recent studies have demonstrated that,in addition to enhancing the photocatalytic activity,lanthanide-doped TiO2 can also increasethe stability of the most photoactive anatase phase.However,lanthanide-doped TOCs remain rare.To the best of our knowledge,only tenlanthanide-doped TOCs have been reported,and the largest number of lanthanide ions doped in TOCs is 2.Furthermore,only one literature was investigated on the property of the lanthanide-doped TOCs.Based on the above background,we reported in this dissertation the syntheses,crystal structures,fluorescent,photoelectric chemical and photocatalytic properties of the lanthanide-doped TOCs.The specific contents are as follows:1.A series of lanthanide-doped TOCs,Ln2Ti4(Ln = Eu(1),Gd(2),and Sm(3));Ln5Ti4(Ln = Ce(4),Eu(5),Sm(6),Pr(7)and Nd(8));LngTi10(Ln = Eu(9)and Sm(10)),were synthesized through thesolvothermal reaction of rare-earth salts,Ti(OiPr)4 and 4-tert-butylbenzoic acid ligand.The phosphorescent life times of the clusters were 1.08923 ± 0.01313 ms for 1,10652 ± 0.01049 ms for 5 and 1.26905 ± 0.00746 ms for 9.The quantumyields(QY)in toluene were 7.050%,29.63%and 45.33%for 1,5 and 9,respectively.2.Five lanthanide-doped TOCs,[Ln8Ti10(?3-O)14(tbba)34(Ac)2(H2O)4-(THF)2]·2Htbba(Ln = Eu(9),Sm(10),Gd(11),Nd(12),Tb(13);Htbba =4-tert-butylbenzoic acid,Ac" = acetate),were synthesized through a solvothermal reaction ofLn(Ac)3-xH2O,Ti(OiPr)4 and 4-tert-butylbenzoic acid ligand.Investigation on photocatalytic activity of 9-11 revealed that these stable compounds are efficient catalysts for photoinduced water oxidation.The Faraday efficiencies are 77.3%for 9,53.7%for 10,and 46.5%for 11,the turnover numbers(TONs)are 2920 for 9,631 for 10,and 633 for 11,and the turnover frequencies(TOFs)are 973 h-1 for 9,210 h-1 for 10,and 211 h-1 for 11.The differences in the photocatalytic activity among these compounds are related to the differences in their band gaps.3.A lanthanide-doped TOC,Ce6Ti6(OH)8O6(CH3COO)4((CH3)3CCOO)18(THF)3(H2O)6(14),was synthesized through a solvothermal reaction ofcerium(III)sulfate octahydrate and Pivalic acid ligand.UV/vis spectroscopy of thecluster reveals that the optical band gap is red-shifted with respect to anatase phase reported.Investigation on the photocatalytic property of cluster 14 revealed that its photocatalytic effect is significantly better than that of P25.4.A new lanthanide-doped TOC,La3Ti5(?3-O)6(C5H5O2)2(C11H13COO)15(THF)](15),was synthesized through a solvothermal reaction of lanthanum acetylacetone and with 4-tert-butylbenzoic acid ligand.The light induced electron transfer in the cluster 15 under the simulated solar spectrum was discussed.