The direct oxidation of CH₄ to C₂H₅OH is attractive but challenging owing to the intricate processes involving carbon-chain growth and hydroxylation simultaneously. The inherent difficulty arises from the strong tendency of CH₄ to overoxidize in the commonly used pressurized powder suspension systems rich in reactive oxygen radicals (ROR), which are specifically designed for CH₄ concentration and activation. Meanwhile, the strong tendency of nucleophilic attack of potent ROR on the C–C bond of the resulting product C₂H₅OH ultimately leads to a higher selectivity for C1 oxygenates. This study addresses this multifaceted issue by designing a three-phase interface based on a hydrophilic floating Fe(III)-cross-linked macroporous alginate hydrogel film encapsulated with C₃N₄ [Fe(III)@ACN] to simultaneously enhance the accessibility of H₂O and CH₄ molecules to the active sites and species within the macroporous channel. The hydrophilic properties of Fe(III)@ACN allow the in situ production of H₂O₂ from C₃N₄ through the water oxidation reaction under irradiation. The concurrent photoinduced Fe(II) triggers Fenton reaction with H₂O₂ to produce ^•OH. The enhanced mass transfer of CH₄ at the three-phase interface ensures the efficient formation of ^•CH₃ by reacting with ^•OH, ultimately facilitating carbon-chain growth in the conversion pathway from CH₄ to CH₃OH and finally to C₂H₅OH with ^•CH₃ and ^•OH present in comparable concentrations. Thus, the Fe(III)@ACN catalyst exhibits a remarkable 96% selectivity for alcohol, achieving a 90% selectivity for C₂H₅OH in the alcohol products. The C₂H₅OH production rate reaches 171.7 μmol g^–1 h^–1 without the need for precious-metal additive.

中文翻译：

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浓度匹配的羟基和甲基自由基在三相界面处将甲烷光催化转化为乙醇

_{CH 4}直接氧化为C ₂ H ₅ OH 很有吸引力，但由于同时涉及碳链增长和羟基化的复杂过程而具有挑战性。固有的困难源于CH ₄在常用的富含活性氧自由基(ROR)的加压粉末悬浮液系统中过度氧化的强烈倾向，该系统是专为CH ₄浓缩和活化而设计的。同时，有效的ROR对所得产物C ₂ H ₅ OH的C-C键的强烈亲核攻击倾向最终导致对C1含氧化合物的更高选择性。本研究通过设计基于亲水性浮动 Fe(III) 交联大孔藻酸盐水凝胶膜的三相界面解决了这个多方面的问题，该膜被 C ₃ N ₄ [Fe(III)@ACN] 封装，同时增强了H ₂ O和CH ₄分子到达大孔通道内的活性位点和物质。 Fe(III)@ACN的亲水特性允许在辐射下通过水氧化反应由C ₃ N ₄原位产生H ₂ O ₂ 。同时发生的光诱导 Fe(II) 引发与 H ₂ O ₂的 Fenton 反应，生成^· OH。 CH ₄在三相界面处增强的传质确保了通过与^{· OH 反应有效形成·} CH _{3 ，最终促进从CH 4}到CH ₃ OH并最终到C ₂ H的转化途径中的碳链生长₅ OH，其中^• CH ₃和^• OH 以相当的浓度存在。因此，Fe(III)@ACN催化剂对醇表现出高达96%的选择性，对醇产物中的C ₂ H ₅ OH实现了90%的选择性。无需贵金属添加剂，C ₂ H ₅ OH产率可达171.7 μmol g ^–1 h ^{–1 。}