Photocatalytic selective oxidation of p-xylene with O₂ offers a mild pathway to synthesize p-methyl benzaldehyde (p-MBA), which is one of the primary precursors in the manufacture of fine chemicals. Here, we report that Au/WO_x/TiO₂ photocatalyst selectively catalyzes the oxidation of p-xylene to p-MBA with 88.6% selectivity at 1.0% conversion, the formation of CO_x is suppressed to 0.8%. Kinetic experiments indicate that p-methylbenzyl alcohol and p-MBA are initial products. p-Methylbenzyl alcohol is further oxidized to form p-MBA, p-methylbenzyl acid and CO_x; p-MBA is further oxidized to p-methylbenzyl acid and CO_x. On TiO₂ surface, p-methylbenzyl alcohol is more prone to directly combust to CO_x by O₂^–. Loading of WO_x can weaken the adsorption ability of p-methylbenzyl alcohol on the catalyst surface to avoid the combustion. Meanwhile, WO_x and Au can facilitate the separation of photo-generated carriers to attain high activity and suppress the O₂^– formation to obtain high selectivity.

O ₂对二甲苯的光催化选择性氧化为合成对甲基苯甲醛 ( p -MBA)提供了一种温和的途径，它是精细化学品制造中的主要前体之一。在这里，我们报道了Au/WO _x /TiO ₂光催化剂选择性催化对二甲苯氧化为p - MBA，选择性为88.6%，转化率为1.0%，CO _x的形成被抑制到0.8%。动力学实验表明对甲基苯甲醇和对MBA是初始产物。对甲基苄醇进一步氧化生成对-MBA、对-甲基苄基酸和CO _x；p -MBA 被进一步氧化成对甲基苄基酸和CO _x。在TiO ₂表面，对甲基苯甲醇更容易被O ₂ ^{-直接燃烧成CO} _x。负载WO _x可以减弱对甲基苄醇在催化剂表面的吸附能力，避免燃烧。同时，WO _x和 Au 可以促进光生载流子的分离以获得高活性并抑制O ₂ ^-形成以获得高选择性。