The research team first synthesized the single-phase crystal structure of ZnFe₂O₄ spinel. The ZnFe₂O₄ oxide sample was activated in situ prior to the CO₂ hydrogenation reaction. The experimental observation showed that more than 97% of the reaction products consisted of methanol and ZnFe₂O₄ catalyst exhibited a high CH₃OH selectivity and CO₂ conversion. ZnO and Fe₂O₃ oxides were synthesized and tested for comparison, which showed a much lower CO₂ conversion and CH₃OH selectivity. 

These results indicated the ZnFe₂O₄ spinel phase enabled high methanol selectivity during CO₂ hydrogenation. The experimental analysis suggested the oxygen vacancy on the surface of ZnFe₂O₄ spinel is the active site for CO₂ and H₂ activation. 

Besides, the research team found that spinel ZnFe₂O₄ plays a vital role in the formation of oxygenates from CO₂ hydrogenation, whereas the formation of the Fe₅C₂ phase facilitates both carbon chain growth and the insertion of C1 oxygen-containing intermediates to yield C₂₊OH after further hydrogenation, which greatly increases the selectivity of C₂₊OH in addition to olefins. Introducing Fe₅C₂ phase to the formation of the ZnFe₂O₄/Fe₅C₂ interface greatly promoted C₂₊OH selectivity in oxygenates to 98.2%, giving a high C₂₊OH productivity and an unprecedented C₃₊OH yield of 5.3%. 

Moreover, theoretical calculations revealed the role of the ZnFe₂O₄/Fe₅C₂ interface in the C-C coupling. The ZnFe₂O₄/Fe₅C₂ interface drives selective transformation to C₂₊OH by promoting the facile migration of alkyl species to the interface and coupling with CHO* species, which contributes to the breaking of the Anderson-Schulz-Flory (ASF) distribution and results in a much lower methanol selectivity than expected. 

This work demonstrates a new strategy for selectivity tuning in alcohol synthesis by crystal structure engineering.