| Polyoxometalates have potential applications in materials,catalysis,science,biomedicine and other fields due to their rich and diverse structures and unique properties.With the continuous improvement of the scientific level,the development of polyoxometalates has been greatly promoted,and more and more polyoxometalates have been determined.Many polyoxometalates with novel structures have been synthesized,especially the research on sandwich polyoxometalates is increasing.In recent years,titanium-substituted polyoxometalates have attracted more and more people because of their excellent semiconductor Ti O2 properties.However,the development of titanium-containing molybdates lags behind,mainly due to the instability of their structure.In addition,titanium oxide clusters modified by small organic molecules have become a research hotspot due to their novel structures and properties.Therefore,this thesis designed and synthesized a novel structure of sandwich-type titanium-containing molybdate and organic ligand-modified titanium oxide clusters,and explored its synthesis conditions and related properties.In this paper,in-situ self-assembly method was used to synthesize 7 compounds in aqueous solution.The compounds were characterized by elemental analysis,single crystal X-ray diffraction,infrared spectroscopy,thermogravimetry and other methods,and the semiconductor and fluorescent properties of the compounds were discussed,Photocatalytic properties and electrocatalytic properties.1.In the conventional aqueous solution,two cases of water-soluble sandwich titanium antimony molybdate 1-2 were synthesized,the molecular formula is as follows:（NH4）8[（CH3）4N]2[Ti2(Sb Mo7O27)2]·22H2O（1）（NH4）5[Himi]5[Ti2(Sb Mo7O27)2]·14H2O（2）The crystal structure shows that compounds 1 and 2 all contain the same{Ti2(Sb Mo7O27)2}sandwich unit.The presence of crystal water and NH4+makes many strong hydrogen bonds formed in the crystal structure,which indicates that hydrogen bonds assist the formation of the crystal structure.Cyclic voltammetry test shows its redox characteristics in aqueous solution,and photoelectrocatalytic reduction of bisphenol A shows that it can be used as a good photoelectrochemical sensing material.2.In a conventional aqueous solution,using As2O3 and（NH4）6Mo7O24·4H2O as raw materials,two sandwich-type titanium-containing arsenic molybdates 3-4 were synthesized.The molecular formula is as follows:（NH4）8[（CH3）4N]2[Ti2(As Mo7O27)2]·16H2O（3）（NH4）8[Himi]2[Ti2(As Mo7O27)2]·19H2O（4）Compound 3 and 4 are two{As Mo7O27}units connected by{Ti Ti′O10}subunits to form a"sandwich"sandwich structure.Through the test of solid ultraviolet diffuse reflectance spectroscopy and Mott-Schottky curve,it is obtained that both are n-type semiconductors,with electrical conductivity,and photocatalytic degradation of methyl orange.The results show that compounds 3-4 is a potential photocatalyst.3.In conventional aqueous solutions,synthesize titanium oxide clusters 5-6 with salicylic acid and nitrilotriacetic acid as ligands,and further use compound 5 as the pre-material to obtain compound 7,with the following molecular formula:[C4H12N]2[Ti（C7H4O3）3]·1.5H2O（5）K4[Ti ON（CH2COO）3)]4·3H2O（6）（NH4）16[Mo36O116]·26H2O（7）In compound 5,there is a mononuclear structure.Ti connects 6 oxygen atoms from salicylic acid to form a twisted space structure.Compound 6 is a tetranuclear titanium oxide cluster composed of{Ti4O4}units.[Ti ON（CH2COO）3)]-coordinates with K+to form a two-dimensional layered structure.Compound 7 is composed of two{MO18}units through inversion The ring structure formed.Electrocatalytic properties studies show that compounds5-7 have a certain catalytic effect on nitrite. |
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