Dimethyl ether (DME) production has been attracting significant research attention for its broad uses as an important chemical feedstock as well as a promising fuel. Herein we report CO₂ direct hydrogenation to produce DME using a new CIZO–SAPO bifunctional catalytic structure, which consists of Cu–In–Zr–O (CIZO) mixed oxide sites toward methanol synthesis and SAPO-34 zeolite sites for intermediate dehydration to DME. Compared with CIZO, a significant increase in CO₂ conversion was achieved by simply mixing CIZO and SAPO, indicating the existence of synergy within the bifunctional catalyst. The study of mixing ratios and methods further confirmed the synergetic effect being proximity dependent. Mechanistic insight was obtained by conducting in-situ DRIFTS analyses. Variation in the proximity between CIZO and SAPO was discovered to alter the reaction pathways. When CIZO and SAPO were more closely contacted, DME could be generated via a shortcut methoxy–DME pathway instead of a typical methoxy–methanol–DME route, resulting in more efficient DME formation. The shortcut pathway was suppressed with an increase in distance between the two components. Therefore, it is proposed that the synergetic effect that leads to boosted DME formation in the bifunctional catalyst is determined by the altered reaction pathway which is controlled by the proximity between CIZO and SAPO active sites. The adjacency of CIZO and SAPO facilitates migration of methoxy intermediates from the former to the latter, so that DME would be formed directly without a need of methanol formation. This study unveils the synergetic mechanism within bifunctional catalyst in DME synthesis that would provide guidance to new catalyst research.

中文翻译：

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在CIZO-SAPO双功能催化剂中将CO ₂加氢成DME的邻近驱动协同作用得到阐明

二甲醚（DME）的生产作为一种重要的化学原料以及一种有前途的燃料，已引起了广泛的研究关注。本文中，我们报告了使用新的CIZO-SAPO双功能催化结构进行的CO ₂直接加氢生产DME，该结构由向甲醇合成的Cu-In-Zr-O（CIZO）混合氧化物位点和中间脱水成DME的SAPO-34沸石位点组成。与CIZO相比，CO ₂显着增加只需将CIZO和SAPO混合即可实现转化，这表明双功能催化剂中存在协同作用。对混合比例和方法的研究进一步证实了协同效应是接近性的。通过进行原位DRIFTS分析获得了机械方面的见解。发现CIZO和SAPO之间的接近度变化可改变反应路径。当CIZO和SAPO更紧密地接触时，可以通过捷径的甲氧基-DME途径而不是典型的甲氧基-甲醇-DME途径生成DME，从而更有效地形成DME。随着两个组件之间距离的增加，捷径途径受到抑制。因此，有人提出，在双功能催化剂中促进DME形成的协同作用是由改变的反应途径决定的，该反应途径受CIZO和SAPO活性位点之间的接近度控制。CIZO和SAPO的邻接促进了甲氧基中间体从前者向后者的迁移，从而可以直接形成DME而无需形成甲醇。这项研究揭示了DME合成中双功能催化剂内部的协同机理，这将为新催化剂的研究提供指导。