Insight into Carbocation‐Induced Noncovalent Interactions in the Methanol‐to‐Olefins Reaction over ZSM‐5 Zeolite by Solid‐State NMR Spectroscopy

• Published in: Angewandte Chemie International Edition Vol. 60; no. 51; pp. 26847 - 26854
• Main Authors: Wang, Chao, Chu, Yueying, Hu, Min, Cai, Wenjin, Wang, Qiang, Qi, Guodong, Li, Shenhui, Xu, Jun, Deng, Feng
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 13.12.2021
• Edition: International ed. in English
• Subjects: Alkanes; Alkenes; carbocations; Cations; Chemical bonds; Dipoles; Functional groups; Hydrocarbons; Intermediates; Magnetic resonance spectroscopy; Methanol; methanol conversion; NMR; NMR spectroscopy; noncovalent interactions; Nuclear magnetic resonance; Selectivity; solid-state NMR spectroscopy; Spectroscopy; Spectrum analysis; Theoretical analysis; Zeolites
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.202112948

Carbocations such as cyclic carbenium ions are important intermediates in the zeolite‐catalyzed methanol‐to‐olefins (MTO) reaction. The MTO reaction propagates through a complex hydrocarbon pool process. Understanding the carbocation‐involved hydrocarbon pool reaction on a molecular level still remains challenging. Here we show that electron‐deficient cyclopentenyl cations stabilized in ZSM‐5 zeolite are able to capture the alkanes, methanol, and olefins produced during MTO reaction via noncovalent interactions. Intermolecular spatial proximities/interactions are identified by using two‐dimensional 13C–13C correlation solid‐state NMR spectroscopy. Combined NMR experiments and theoretical analysis suggests that in addition to the dispersion and CH/π interactions, the multiple functional groups in the cyclopentenyl cations produce strong attractive force via cation‐induced dipole, cation–dipole and cation–π interactions. These carbocation‐induced noncovalent interactions modulate the product selectivity of hydrocarbon pool reaction. Multiple noncovalent interactions involving cyclopentenyl cations in the methanol‐to‐olefins (MTO) reaction over ZSM‐5 zeolite were identified by using two‐dimensional solid‐state NMR spectroscopy. It was found that the hydrocarbon pool reaction is modulated by carbocation‐induced noncovalent interactions.