Amorphous/crystalline HTiNbO membranes for efficient confined flow synthesis of acetate ester flavours.

Ideal laminar membrane reactors (LMR) necessitate the rational construction of 2D nanoconfined channels and regulation of microenvironment. The intrinsic structure-activity relationship of laminar membrane reactors essentially remains unclear. Herein, amorphous/crystalline HTiNbO nanosheets (NS) with abundant oxygen vacancy (V) are successfully prepared and stacked as 2D sub-nanoconfined membrane flow reactors with different interlayer spacings. When the interlayer spacing is decreased to 11.0 Å, the representative HTiNbO membrane exhibits impressive conversion of ≈ 100% within 26.6 s and turnover number of up to 306.42 for the esterification of benzyl alcohol at 23 °C. The combination of structural characterizations and theoretical calculations reveals that the synergistic effect of V and sub-nanoscale confinement greatly promotes the adsorption and orbital symmetry matching of reactants, and reduces the overall energy barrier. Furthermore, the HTiNbO LMR is accessible for other alcohol derivatives, indicating the efficient and green synthesis of acetate ester flavours under mild conditions. This work demonstrates the promising potential of the metal oxide nanosheets to create inorganic laminar membrane reactors for continuous organic synthesis.