The conversion of natural gas (mainly methane) to more valuable compounds is an attractive topic in energy field. While heterogeneously catalytic conversion of methane with hydrogen peroxide (H₂O₂) has been extensively studied, in‐depth study on similar homogeneous systems is lacking. In this work, FeCl₃ was demonstrated as an excellent homogeneous catalyst for direct oxidation of methane in the presence of H₂O₂ at near ambient temperature (50°C) in water, with significant yields of methanol (1972.2 μmol/g_cat) and formic acid (33 273.5 μmol/g_cat) and a high turnover frequency (TOF) of 5.7 hours⁻¹. The superiorities of both the cation (Fe³⁺) and the anion (Cl⁻) were revealed by studying the cation and anion effects in comparison with CoCl₂ and NiCl₂ (TOF of 0.035 and 0 hour⁻¹, respectively) as well as Fe(NO₃)₃ and FeBr₃ (TOF of 3.3 and 0.73 hour⁻¹, respectively). Furthermore, it was found that the hydrated ferryl ion [(H₂O)₅Fe^IVO]²⁺ could be the major active species for the activation of CH₄ and the formation of CH₃OH, whereas the hydroxyl radicals (·OH) were responsible for the formation of HCOOH, CO and CO₂. Moreover, theoretical study based on density function theory (DFT) suggested that the cation effect could be related to the Gibbs free energies for CH₄ activation on their corresponding active species. Meanwhile, the anions affect the performance mainly by the structural features.

中文翻译：

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在接近环境温度的条件下，水中的氯化铁（III）将甲烷直接转化为含氧化合物

天然气（主要是甲烷）向更有价值的化合物的转化是能源领域的一个有吸引力的话题。尽管对甲烷与过氧化氢（H ₂ O ₂）的非均相催化转化进行了广泛的研究，但缺乏对相似的均相系统的深入研究。在这项工作中，FeCl ₃被证明是一种出色的均相催化剂，可在存在H ₂ O ₂的情况下，在接近环境温度（50°C）的水中直接甲烷甲烷氧化，并产生大量甲醇（1972.2μmol/ g _cat）甲酸（33 273.5μmol/ g _cat）和5.7小时^-1的高周转频率（TOF）。两个阳离子（Fe的优势³⁺）和阴离子（氯^- ）通过用氯化钴研究相比阳离子和阴离子的影响显露₂和的NiCl ₂（0.035 TOF和0小时^-1，分别地）以及Fe（NO ₃）₃和FeBr ₃（TOF分别为3.3和0.73小时^-1）。此外，还发现水合亚铁离子[（H ₂ O）₅ Fe ^IV O] ²⁺可能是CH ₄活化和CH ₃形成的主要活性物质。OH，而羟基（·OH）负责形成HCOOH，CO和CO ₂。此外，基于密度泛函理论（DFT）的理论研究表明，阳离子效应可能与相应的活性物种上CH ₄活化的吉布斯自由能有关。同时，阴离子主要通过结构特征影响性能。