Direct structural identification of carbenium ions and investigation of host–guest interaction in the methanol to olefins reaction obtained by multinuclear NMR correlations

Abstract

Probing and determining the intermediates formed during catalytic reactions in heterogeneous catalysis are strong challenges. Using ¹³C labelling and two dimensional ¹³C–¹³C through-bond NMR correlations, we directly reveal the structures of a range of carbenium ion species formed during the conversion of methanol to olefins on acidic H-ZSM-5 zeolite by mapping the carbon–carbon bond connectivities. Additionally, we use ¹³C–²⁷Al and ²⁹Si–¹³C through-space NMR experiments to probe the interactions between the confined carbon species (including carbenium ions) and the framework of the zeolite, which quantitatively provide an estimate for the carbon–aluminium and carbon–silicon distances, respectively.