Fig. 6: A summary of control experiments.

The catalytic performance of the standalone zeolite-mediated conversion of a (¹²C)ethylene and b fully enriched ¹³CO and (¹²C)ethylene at 30 bar, 375 °C, and 10,000 mL · g⁻¹ · h⁻¹ under hydrogen-rich environment at a time on stream of 2 h (i.e., without any Fe₂O₃@KO₂ phase) (also see Supplementary Fig. 14). c 1D ¹³C direct excitation MAS solid-state NMR spectra on all four zeolites, collected after the control experiments involving both ¹³CO and ¹²C₂H₄ in the reactant feed. Due to the selective isotope enrichment of ¹³CO in the reactant feed, DE experiments can only be correlated to the ¹³CO consumption during catalysis. The broad nature of DE experiments (except FER) implying that ¹³CO predominantly converted to the rigid species only (also see Supplementary Figs. 15 and 16 for details, MAS magic angle spinning). d The spectral identification of methyl acetate was observed on the postreacted FER zeolite via ¹³C-¹³C correlation spectra, where the carbons were polarized through direct excitation and ¹³C-¹³C mixing was achieved through proton-driven spin diffusion (PDSD) (also see Supplementary Fig. 17). The respective full-range spectra, as well as experimental details, are included in Supplementary Information.