Stable CO<sub>2</sub> Hydrogenation to Methanol by Cu Interacting with Isolated Zn Cations in Zincosilicate CIT-6
Yu Gao, Yonghui Fan, Hao Zhang, Peerapol Pornsetmetakul, Brahim Mezari, Jorden Wagemakers, Mahesh Ramakrishnan, Konstantin Klementiev, Nikolay Kosinov, Emiel J. M. Hensen
Abstract
High Resolution Image Download MS PowerPoint Slide The catalytic conversion of carbon dioxide (CO 2 ) to methanol over Cu/ZnO catalysts is expected to become valuable for recycling CO 2 . The nature of the Cu–Zn interplay remains a subject of intense debate due to many different Zn species encountered in Cu/ZnO catalysts. In this study, we designed a Cu–Zn catalyst by ion-exchanging Cu into CIT-6, a crystalline microporous zincosilicate with the BEA* topology. The catalyst exhibited high and stable CO 2 hydrogenation rate to methanol. In contrast, its aluminosilicate counterparts Cu-Beta and CuZn-Beta mainly converted CO 2 to CO. Operando X-ray absorption spectroscopy combined with X-ray diffraction confirmed the stability of Zn cations in the zincosilicate framework during reduction in H 2 and reaction in CO 2 /H 2 . The active phase consisted of highly dispersed Cu particles. These particles located near isolated Zn 2+ species represent a different type of active site for methanol synthesis than the active phases proposed for Cu–Zn catalysts, such as Cu–Zn alloy particles and Cu particles decorated with ZnO x . In situ IR spectroscopy showed the formation of Zn-formate species during CO 2 hydrogenation, indicating that Zn 2+ ions stabilize formate as a reaction intermediate in the hydrogenation of CO 2 to methanol.