Preparation of Photocatalysts in Micro-pores of Zeolite and Their Reaction Dynamics

在沸石中设计离子和/或簇大小的催化剂是特别令人感兴趣的，因为这些迷人的载体提供独特的纳米级孔系统、不寻常的内表面形貌和离子交换能力。沸石的孔结构不仅允许反应物分子扩散到聚合物中，从而可以接触锚定在沸石空腔内的催化剂，而且还可以在随后的离子和/或簇生长期间保持完整。特定光催化反应所需空间的修改是重要的。在改性反应空间中，可以预期在正常催化体系中无法实现的独特光催化性能。研究发现，在275 K下，在CO_2和H_2O的存在下，活性氧化钛催化剂经紫外光照射后，可以实现CO的光催化还原 ...更多信息 _2。用原位光致发光、UV-Vis、XAFS、ESR、FT-IR和XPS等光谱技术研究了TiO_2催化剂上CO_2与H_2O光催化还原反应的特征.结果表明，在TiO_2粉末上反应主要生成甲烷，而在高分散的多孔玻璃和沸石上的TiO_2催化剂上反应主要生成CH_4，CH_3OH，主要产物为C_2-化合物和CO。phptp催化反应的产率与催化剂类型、CO_2/H_2O值和反应温度密切相关。对该体系的原位光谱研究表明，H_2O光催化还原CO_2的反应与其高得多的电荷转移激发态反应活性有关，(Ti表面上形成的四面体配位的钛氧化物物种的^<3+>-O^-）^<3*>。通过对反应中间产物Ti^<3+>、H原子和C自由基的检测，从分子水平上提出了H_2O光催化还原CO_2的反应机理。少

It is of special interest to design the ion and/or cluster size catalysts within the zeolites because these fascinating supports offer unique nano-scaled pore systems, unusual internal surface tipology, and ion-exchange capacities. The pore structure of the zeolite not only allows for reactant molecules to diffuse into the ppre where in can access the catalyst anchored within the zeolite cavities, but also can remain intact during subsequent ion and/or cluster growth. The modification of the space required for a specific photocatalytic reactions is important. Unique photocatalytic properties which cannot be realized in normal catalytic systems can be expected in modified reaction spaces. Zeolites with well-defined nano-pore structure provide one of the most promising modified spaces for photocatalytic reactions.In the present study, it was found that UV-irradiation of the active titanium oxide catalysts in the presence of CO_2 and H_2O at 275 K led to the photocatalytic reduction of CO … More _2. The characteristic features of the photocatalytic reduction of CO_2 with H_2O on the active titanium oxide catalysts were investigated by in situ photoluminescence, UV-Vis, XAFS,ESR,FT-IR and XPS spectroscopic techniques.The reactions on TiO_2 powders produced methane as the major product, while, on the highly dispersed titanium oxide anchored on a porous glass and zeolites the formation of CH_4, CH_3OH,C_2-compounds and CO was observed as the major products. The yields of the phptpcatalytic reactions strongly depended on the type of catalysts, the values of CO_2/H_2O and the reaction temperatures. In situ spectroscopic studies of the system indicated that the photocatalytic reduction of CO_2 with H_2O is linked to the much higher reactivity of the charge transfer excited state, i.e., (Ti^<3+>-O^-)^<3*> of the tetrahedral coordinated titanium oxides species formed on the surfaces. Based on the detection of reaction intermediate species such as Ti^<3+>, H atoms, and C radicals, reaction mechanism for the photocatalytic reduction of CO_2 with H_2O has been proposed on a molecular scale. Less