The Co₃O₄ spinel is one of the most promising transition metal oxide (TMO) catalysts for volatile organic compound (VOC) treatment. Substituting effects have usually been utilized to improve the catalytic performance of the Co₃O₄ spinel. In this study, Cu- and Ni-substituted Co₃O₄ catalysts derived from mixed metal–organic frameworks (MMOFs) retained similar spinel structures but exhibited improved and reduced performance for o-xylene oxidation, respectively. Physicochemical characterization and DFT calculations revealed that Cu and Ni substitution into the Co₃O₄ spinel varied the valence (Co³⁺/Co²⁺) and geometry (Co_Oh/Co_Td) distributions of Co cations through different partial electron transfer and substitution sites. The higher Co³⁺/Co²⁺ and Co_Oh/Co_Td ratios of the CuCo₂O₄ catalyst contributed to the superior reducibility and oxygen mobility, which facilitated the oxidation of intermediates at lower temperatures in the catalytic oxidation of o-xylene. Meanwhile, the NiCo₂O₄ catalyst with lower Co³⁺/Co²⁺ and Co_Oh/Co_Td ratios could not completely oxidize intermediates under the same conditions due to inferior redox properties. Therefore, the CuCo₂O₄ catalyst showed superior catalytic activity and stability to the NiCo₂O₄ catalyst for the catalytic oxidation of o-xylene. This work provides insights into the synthesis of substituted Co₃O₄ catalysts from MMOFs and mechanism of substituting effects, which might guide the design of efficient TMO catalysts for VOC treatment.

中文翻译：

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改变 CoOh/CoTd 和 Co3+/Co2+ 比率的 Cu-和 Ni-取代的 Co3O4 催化剂对 VOC 的完全催化氧化性能的改进和降低

Co ₃ O ₄尖晶石是用于挥发性有机化合物（VOC）处理的最有前途的过渡金属氧化物（TMO）催化剂之一。取代效应通常被用来提高Co ₃ O ₄尖晶石的催化性能。在这项研究中，来自混合金属有机骨架（MMOF）的Cu 和 Ni 取代的 Co ₃ O _{4催化剂保留了相似的尖晶石结构，但分别表现出改善和降低了}邻二甲苯氧化性能。物理化学表征和 DFT 计算表明，Cu 和 Ni 取代到 Co ₃ O ₄尖晶石中改变了化合价（Co^{Co 阳离子通过不同的部分电子转移和取代位点的3+} /Co ²⁺ ) 和几何 (Co _Oh /Co _Td ) 分布。_{CuCo 2} O ₄催化剂较高的Co ³⁺ /Co ²⁺和Co _Oh /Co _Td比有助于优异的还原性和氧迁移率，这有利于在邻二甲苯催化氧化中在较低温度下氧化中间体。同时，NiCo ₂ O ₄催化剂具有较低的 Co ³⁺ /Co ²⁺和 Co _Oh /Co_{由于氧化还原性能较差， Td}比率不能在相同条件下完全氧化中间体。因此，CuCo 2 O 4 催化剂对邻二甲苯的催化氧化表现出优于NiCo ₂ O ₄催化剂的催化活性_和稳定性_。这项工作为从 MMOF 合成取代的 Co ₃ O ₄催化剂和取代效应的机理提供了见解，这可能会指导设计用于 VOC 处理的高效 TMO 催化剂。