Cu-Doped Layered Double Hydroxide Nanotubes For CO ₂ Reduction under Supercritical Conditions

Layered double hydroxides are structurally versatile materials whose chemical and electronic properties can be tuned to yield efficient heterogeneous catalysts and catalyst precursors for green chemistry applications, including sustainable fuel production for the methanol economy. We demonstrate that chemical tailoring via copper incorporation into ZnAlEu LDHs, combined with soft templating using a P-123 surfactant, yields well-defined nanotubular structures with markedly enhanced thermo- and photocatalytic performance in CO2 hydrogenation to methanol. Eu3+ incorporation enabled the nanotubular morphology and induced a 5-fold enhancement in the surface area of the LDHs, while subsequent Cu doping introduced active catalytic sites and further increased the surface area, reaching a maximum of 184 m2.g–1 at an optimal Cu loading of 20%. Under visible light, these materials demonstrated methanol yields significantly higher than nonhierarchical, flake-like LDHs, with a high selectivity attributed to the extended residence time of intermediates within the interlayer spaces. Thermocatalytic CO2 hydrogenation in flow reactors further confirmed the superior activity and selectivity of the Cu20%-P123 catalyst, achieving a methanol yield of 55 mg·gat–1·h–1, outperforming conventional Cu-ZnO-Al2O3-based catalysts. These findings highlight the critical role of composition tuning and morphology control in enhancing the catalytic activity of LDH-based materials, offering a promising route for the sustainable valorization of CO2.