Selective oxidation of alcohols to aldehyde or ketone is a fundamental reaction in organic synthesis. Herein, a self-catalyzed Pickering emulsion microreactor (PEM) was designed for the selective oxidation of benzyl alcohol (BzOH) to benzaldehyde (BzH) using peroxymonosulfate (PMS) as an oxidant. Featuring inherent pyridinic N and pyridine N-oxide species, Enteromorpha prolifera-derived biochar displayed particular super-amphiphilicity, able to serve as an emulsifier and catalyst simultaneously in the PMS-based PEM (PPEM) system. The results showed that, without extra additives, the PPEM system could 100% selectively oxidize 2.88 mM of BzOH to BzH (yield: 90.4%) within 30 min at room temperature. After systematic and theoretical studies, we found that radical (O₂˙⁻) and non-radical (¹O₂ and mediated electron transfer) oxidation routes were responsible for the selective BzOH oxidation to BzH, where the reaction energy barrier for the oxidation of BzOH by ¹O₂ (18.0 kcal mol⁻¹) is lower compared to that of O₂˙⁻ (25.8 kcal mol⁻¹). Overall, the rationally fabricated biochar with special surface wettability and catalytic activity offers a novel emulsion self-catalysis route to achieve the selective oxidation of alcohol.

中文翻译：

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自催化Pickering乳液微反应器加速苯甲醇选择性氧化为苯甲醛


醇选择性氧化为醛或酮是有机合成中的基本反应。在此，设计了一种自催化Pickering乳液微反应器（PEM），用于使用过一硫酸盐（PMS）作为氧化剂将苯甲醇（BzOH）选择性氧化为苯甲醛（BzH）。浒苔衍生的生物炭具有固有的吡啶N和吡啶N-氧化物物种，表现出特殊的超两亲性，能够在基于PMS的质子交换膜（PPEM）系统中同时充当乳化剂和催化剂。结果表明，在没有额外添加剂的情况下，PPEM系统可以在室温下30分钟内100%选择性地将2.88 mM BzOH氧化为BzH（产率：90.4%）。经过系统和理论研究，我们发现自由基（O ₂ ˙ ^- ）和非自由基（ ¹ O ₂和介导的电子转移）氧化途径导致BzOH选择性氧化为BzH，其中氧化的反应能垒¹ O ₂的BzOH (18.0 kcal mol ^-1 ) 比O ₂ ˙ ^- (25.8 kcal mol ^-1 ) 的低。总的来说，合理制备的生物炭具有特殊的表面润湿性和催化活性，为实现醇的选择性氧化提供了一种新颖的乳液自催化途径。