Highly Dispersed Ni Catalyst on Metal–Organic Framework-Derived Porous Hydrous Zirconia for CO₂ Methanation

Abstract

We report the preparation of porous hydrous zirconia by treatment of zirconium-based metal-organic framework (MOF) UiO-66 with a strong base. Microporosity of the original MOF was partially retained in the resultant porous hydrous zirconia. Ni^II centers were then adsorbed onto the OH-rich hydrous zirconia and in situ converted to highly dispersed Ni⁰ for CO₂ hydrogenation to CH₄. The activated catalyst after an induction period showed a turnover frequency of 345 h^-1 or a space-time yield of 5851 mmol·g_Ni^-1·h^-1 with a CH₄ selectivity of over 99%. The catalyst was tested for 100 h on stream, showing only a 4% decrease in activity, and was found to convert atmospheric CO₂ to CH₄ via CO₂ collection through Na₂CO₃/NaHCO₃ cycling. Thermal decomposition of NaHCO₃ released CO₂ for hydrogenation to CH₄, and the resultant Na₂CO₃ absorbed CO₂ from air to form NaHCO₃. This work highlights the opportunity in using MOFs as precursors to prepare highly porous metal oxide/hydroxide supports for solid-gas phase catalysis.