Direct synthesis of dimethyl carbonate (DMC) from CO2 and CH3OH holds significant economic and environmental value. Numerous catalysts have been employed for this reaction, yet further enhancement of its activity requires a deeper understanding of the catalyst's structure-activity relationship and catalytic mechanism. In this study, we utilized structurally well-defined and highly tunable MOF-808 as a research platform. Functionalizing MOF-808 with ethylenediamine (MOF-808-ED) boosted the space time yield of DMC from 3.25 mmol·g-1·h-1 to 7.23 mmol·g-1·h-1. Experimental results demonstrate that the reaction involves acid-base synergistic catalysis, where an appropriate balance of acid-base sites content is crucial for CO2 and CH3OH to produce DMC, as it facilitates the formation of the key intermediates (CH3OCOO*). Additionally, the nucleophilicity of N is stronger than that of O, further promoting the catalyst's enrichment and activation of CO2. Finally, employing in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) testing, we elucidated the mechanism by which the MOF-808-ED catalyst, with -NH2 as base sites and Zr as acid sites, facilitates the synergistic catalysis of the reaction. This study provides insights into the synergistic effects of acid-base sites on the synthesis of DMC from CO2 and methanol, offering valuable guidance for the development of high-performance catalysts.

中文翻译：

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通过酸碱协同作用提高CO2和甲醇直接制碳酸二甲酯的催化活性


由CO2和CH3OH直接合成碳酸二甲酯(DMC)具有显着的经济和环境价值。该反应已使用了许多催化剂，但进一步提高其活性需要更深入地了解催化剂的构效关系和催化机理。在本研究中，我们利用结构明确且高度可调的 MOF-808 作为研究平台。用乙二胺（MOF-808-ED）对MOF-808进行官能化可将DMC的时空产率从3.25 mmol·g-1·h-1提高到7.23 mmol·g-1·h-1。实验结果表明，该反应涉及酸碱协同催化，其中酸碱位点含量的适当平衡对于CO2和CH3OH生产DMC至关重要，因为它有利于关键中间体(CH3OCOO*)的形成。此外，N的亲核性强于O，进一步促进了催化剂对CO2的富集和活化。最后，利用原位漫反射红外傅里叶变换光谱（DRIFTS）测试，阐明了以-NH2为碱位、Zr为酸位的MOF-808-ED催化剂促进反应协同催化的机理。该研究深入探讨了酸碱位点对CO2和甲醇合成DMC的协同作用，为高性能催化剂的开发提供了有价值的指导。