Abstract Benzaldehyde is a highly desirable chemical due to its extensive application in medicine, chemical synthesis and food sector among others. However, its production generally involves hazardous solvents such as trifluorotoluene or acetonitrile, and its conversion, especially selectivity in the aqueous phase, is still not up to expectations. Hence, developing an environmentally benign, synthetic process for benzaldehyde production is of paramount importance. Herein, we report the preparation of a photocatalyst (PW12-P-UCNS, where PW12 = H3PW12O40·xH2O and P-UCNS = phosphoric acid-modified unstack graphitic carbon nitride) by incorporating phosphotungstic acid on phosphoric acid-functionalised graphitic carbon nitride (g-C3N4) nanosheets. The performance of PW12-P-UCNS was tested using the benzyl alcohol photo-oxidation reaction to produce benzaldehyde in H2O, at room temperature (20 °C). The as-prepared PW12-P-UCNS photocatalyst showed excellent photocatalytic performance with 58.3% conversion and 99.5% selectivity within 2 h. Moreover, the catalyst could be reused for at least five times without significant activity loss. Most importantly, a proposed Z-scheme mechanism of the PW12-P-UCNS-catalysed model reaction was revealed. We carefully investigated its transient photocurrent and electrochemical impedance, and identified superoxide radicals and photogenerated holes as the main active species through electron spin-resonance spectroscopy and scavenger experiments. Results show that the designed PW12-P-UCNS photocatalyst is a highly promising candidate for benzaldehyde production through the photo-oxidation reaction in aqueous phase, under mild conditions.

中文翻译：

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杂多酸-固定化石墨氮化碳：苯甲醇在水相中的高效光氧化

摘要 苯甲醛因其在医药、化学合成和食品等领域的广泛应用而成为一种非常受欢迎的化学品。但其生产普遍涉及三氟甲苯或乙腈等有害溶剂，其转化率，尤其是水相选择性，仍达不到预期。因此，开发一种对环境无害的苯甲醛生产合成工艺至关重要。在此，我们报告了通过将磷钨酸掺入磷酸功能化的石墨碳氮化物上来制备光催化剂（PW12-P-UCNS，其中 PW12 = H3PW12O40·xH2O 和 P-UCNS = 磷酸改性的非堆叠石墨碳氮化物（g -C3N4) 纳米片。PW12-P-UCNS 的性能是在室温 (20 °C) 下使用苯甲醇光氧化反应在水中产生苯甲醛来测试的。所制备的 PW12-P-UCNS 光催化剂表现出优异的光催化性能，2 小时内转化率为 58.3%，选择性为 99.5%。此外，催化剂可以重复使用至少五次而不会显着降低活性。最重要的是，揭示了 PW12-P-UCNS 催化模型反应的拟议 Z 方案机制。我们仔细研究了其瞬态光电流和电化学阻抗，并通过电子自旋共振光谱和清除剂实验确定了超氧自由基和光生空穴为主要活性物种。