Confining high-entropy alloys within MOF-derived architectures: a dual-site strategy boosting photothermal CO2 methanation

Abstract

High-entropy alloys (HEAs) offer immense potential for catalytic transformations, yet they suffer from severe sintering and limited active site accessibility due to their typically dense architectures. Herein, we present a facile molten salt-assisted pyrolysis strategy to confine quinary CoNiCuPtPd HEA nanoparticles within a metal–organic framework (MOF)-derived support. By using UiO-66-NH₂ as a precursor, the introduced amino groups are transformed into pyridinic nitrogen sites during pyrolysis, which, along with the abundant oxygen vacancies generated in the ZrO₂ phase, creates a robust porous support UNH-730. Comprehensive characterization studies (XPS and H₂-TPR) confirm that the pyridinic N sites strongly anchor the metal species, facilitating the formation of homogeneously dispersed HEA nanoparticles (∼15 nm) and preventing agglomeration. In situ DRIFTS and catalytic evaluation reveal a synergistic mechanism: basic N sites and oxygen vacancies significantly enhance CO₂ adsorption/activation, while the HEA sites promote H₂ dissociation. Crucially, we demonstrate that light irradiation functions purely as a thermal source rather than triggering photogenerated electron–hole pairs. Consequently, the optimal CoNiCuPtPd@UNH-730 catalyst delivers a remarkable CH₄ yield of 228.36 mmol g⁻¹ h⁻¹ with 77.8% selectivity at 550 °C under photothermal conditions substantially outperforming the ligand-free counterpart. This work establishes a novel paradigm for stabilizing multi-metal HEAs on functionalized porous carbon/oxide composites for energy conversion applications.