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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Matrix effects on the photocatalytic oxidation of alcohols by [nBu _4N]_4W_(10)O_(32) incorporated into sol-gel silica
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Matrix effects on the photocatalytic oxidation of alcohols by [nBu _4N]_4W_(10)O_(32) incorporated into sol-gel silica

机译：溶胶-凝胶二氧化硅中[nBu _4N] _4W_（10）O_（32）对醇光催化氧化的基质效应

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摘要

Two heterogeneous photocatalysts have been prepared by entrapment of [nBu_4N]_4W_(10)O_(32) in a silica matrix, through a sol-gel procedure: SiO_2/W30% and SiO_2/W10% with 30% and 10% of decatungstate, respectively. They are characterized by the presence of micropores of about 7 ? and 15 ? and mesopores of about 25 ?. Due to different preparation procedures, SiO_2/W10% presents a more remarkable porous network than SiO_2/W30%. The morphological features of SiO_2/W30% and SiO_2/W10% differ from those of their parent material SiO_2/W0%, indicating that incorporation of the decatungstate induces a significant modification of the porous texture of the siliceous material. These photocatalysts demonstrate good stability in the oxygen-assisted photooxidation of 1-pentanol and 3-pentanol, which have been chosen as models of primary and secondary aliphatic alcohols. In particular, photoexcitation (λ > 290 nm, 25°C, 760 torr of O _2) leads to conversion of these two substrates to pentanal or 3-pentanone, with a mass balance of about 90%. There is a strong effect of the solid support on the reactivity of the two alcoholic substrates. In particular, oxidation of 1-pentanol with SiO_2/W10% is about four times faster than with [nBu_4N]_4W_(10)O_(32) in homogeneous solution. Preferential adsorption phenomena, due to the hydrophilic character of silica explain the photocatalytic properties of the two heterogeneous systems, because adsorption favours the contact between the photoexcited decatungstate and the primary OH group of 1-pentanol. Moreover, some kind of shape selectivity, due to the microporous structure of the investigated materials, likely contributes to control the conversion yields.
机译：通过溶胶凝胶法将[nBu_4N] _4W_（10）O_（32）截留在二氧化硅基质中，制备了两种非均相光催化剂：SiO_2 / W30％和SiO_2 / W10％以及30％和10％的分解钨酸盐，分别。它们的特征在于存在约7μm的微孔。和15？和约25？的中孔。由于制备方法不同，SiO_2 / W10％比SiO_2 / W30％具有更显着的多孔网络。 SiO_2 / W30％和SiO_2 / W10％的形态特征与它们的母体材料SiO_2 / W0％的形态特征不同，这表明掺入去钨酸盐会明显改变硅质材料的多孔质构。这些光催化剂在1-戊醇和3-戊醇的氧辅助光氧化中表现出良好的稳定性，它们被选作伯和仲脂族醇的模型。尤其是，光激发（λ> 290 nm，25°C，O _2的760托）导致这两种底物转化为戊醛或3-戊酮，质量平衡约为90％。固体载体对两种醇底物的反应性有强烈影响。特别地，在均相溶液中，用SiO_2 / W10％氧化1-戊醇的速度比[nBu_4N] _4W_（10）O_（32）快约四倍。由于二氧化硅的亲水性，优选的吸附现象解释了这两个非均相体系的光催化性能，因为吸附有利于光激发的十碳酸盐和1-戊醇的伯羟基之间的接触。而且，由于所研究材料的微孔结构，某种形状选择性可能有助于控制转化率。

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