Fig. 4: Identification of postreacted zeolite-trapped mobile molecules by 2D MAS solid-state NMR spectroscopy.

¹³C-¹³C correlations in the aliphatic regions on postreacted zeolites a ZSM-5 and ZSM-22 as well as c MOR and FER. b ¹H-¹³C INEPT HETCOR and d ¹³C-¹H HSQC spectra of the aliphatic region from all four postreacted zeolites. e ¹³C-¹³C correlations in the carbonyl regions on postreacted zeolites FER, ZSM-5, and ZSM-22, highlighting the presence of ester and ketones (*: spinning sidebands on ZSM-5). See Supplementary Fig. 12 for the ssNMR spectra of these chemisorbed carbonylated species to verify the respective assignments. f Identified molecular scaffolds. To probe mobile ¹³C-¹H correlations, “through-bond” scalar magnetization transfer was used to polarize the carbons (in b and d), whereas in the ¹³C-¹³C correlation spectra, the carbons were polarized through direct excitation, and ¹³C-¹³C mixing was achieved through proton-driven spin diffusion (PDSD) (in a, c, and e). Spectra of trapped products obtained on respective postreacted zeolites after the hydrogenation of fully isotope-enriched ¹³CO₂ in the reactant feed (¹³CO₂ at 30 bar, 375 °C, H₂/¹³CO₂ = 3, and 10,000 mL · g⁻¹ · h⁻¹ at a time on stream of 48 h). The respective full-range spectra, as well as experimental details, are included in Supplementary Information (MAS magic angle spinning, HETCOR HETeronuclear CORrelation spectroscopy, INEPT insensitive nuclei enhanced by polarization transfer, HSQC heteronuclear single quantum coherence spectroscopy).