The Research Of Photocatalysis Of Porous Glass Immobilized Organotitanium Polymer

The emission reduction of CO₂ and the development of clean energy are important issues to solve the greenhouse effect and energy crisis.The synthesis of methanol from CO₂ catalyzed by sunlight is an incredibly significant research direction.Previously,inorganic semiconductor photocatalysts have been extensively studied by researchers.In recent years,metal-organic frameworks(MOFs)have been widely studied because of their photocatalytic properties.The main characteristics of MOFs are crystallinity and porosity,which are not necessary for photocatalytic activity.MOFs is not a semiconductor and its photogenerated electrons are unstable,because they are difficult to migrate.The turnover frequency(TOF)is too low in photocatalytic research.The preparation of amorphous metal organic polymer is simple,in which the ratio of organic ligands to metal ions is not restricted by the crystal structure and the band gap of the material can be adjusted in a wider range.Therefore,amorphous metal organic polymer has infinite potential in photocatalytic applications.Glass slide immobilized amorphous organotitanium polymer was fabricated by a solvent heating method.Photocatalytic reduction of CO₂ was illuminated under a 300W Xe lamp.The yield of methanol was 751.4?mol for 4 hours of reaction duration and the corresponding turnover frequency(TOF)was 112.0 h^-1.When 0.1 g of NH₂-MIL-125(Ti)was used as catalyst,the yield of methanol was 408.2?mol and the TOF was only 0.21 h^-1.In order to further elucidate the photocatalytic mechanism of amorphous organotitanium polymer,photochromic experiments were carried out.Photochromic experiments confirmed that the amorphous organotitanium polymer contained lifetime of the excited electrons and the recombination rate of excited electrons was slower.In addition,the amorphous organotitanium polymer shows more obvious photocolouration response in EDA aqueous solution than the NH₂-MIL-125(Ti).In order to explore the thermal stability of materials,annealing experiments were carried out at 200?,250?,300?and 350?.Amorphous organotitanium polymer exhibits higher thermal stability.Photocatalytic reduction of CO₂was carried out with300?annealed catalyst.After 4 hours of photocatalysis,the yield of amorphous organic titanium polymer(704.55?mol,105.00 h^-1)showed no significant change compared with that before annealing.The yield of NH₂-MIL-125(Ti)(183.94?mol,0.095 h^-1)was?55%lower than that of fresh NH₂-MIL-125(Ti).Scanning electron microscopy(SEM),X-ray diffraction(XRD),nitrogen adsorption-desorption,infrared spectroscopy(IR),UV-visible absorption spectrum(UV-Vis),fluorescence spectrophotometer(PL)and ultraviolet photoelectron spectroscopy(UPS)were used to characterize the catalysts.The morphology,element composition,metal valence state,photoelectron lifetime and energy band structure of the catalyst were studied.