Direct conversion of methane to acetic acid with high activity and selectivity over non-noble metal-based catalysts under mild reaction conditions remains a grand challenge. Specifically, 1.2Ni-ZSM-5 with 88.9 % isolated Ni sites achieved a high acetic acid yield of 2920 mol/g and a remarkable selectivity up to 82.3 % from methane oxidative carbonylation. Combined with high angle annular dark field scanning transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy analyses, it was revealed that the isolated Ni species with Ni-O moieties anchored in the micropores of ZSM-5 were suggested to be the active sites. The isotopic labeling experiments and monitoring of reaction intermediates demonstrated that CHCOOH was formed via the direct coupling of methyl radicals and carbon monoxide molecules. This work suggests that the well-designed Ni sites can promote the transformation of CH to C oxygenates instead of traditional C oxygenates as main products.

中文翻译：

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锚定在沸石上的孤立镍位点用于从甲烷氧化羰基化直接合成乙酸

在温和的反应条件下，相对于非贵金属基催化剂，以高活性和选择性将甲烷直接转化为乙酸仍然是一个巨大的挑战。具体而言，具有 88.9% 孤立 Ni 位点的 1.2Ni-ZSM-5 实现了 2920 mol/g 的高乙酸产率和高达 82.3% 的甲烷氧化羰基化选择性。结合高角度环形暗场扫描透射电子显微镜、X射线光电子能谱和X射线吸收光谱分析，结果表明，具有Ni-O部分的分离Ni物种锚定在ZSM-5的微孔中成为活性位点。同位素标记实验和反应中间体的监测表明，CHCOOH是通过甲基自由基和一氧化碳分子的直接偶联形成的。这项工作表明，精心设计的 Ni 位点可以促进 CH 转化为 C 含氧化合物，而不是传统的 C 含氧化合物作为主要产物。