Selective Methane Oxidation to Methanol on Cu-Oxo Dimers Stabilized by Zirconia Nodes of an NU-1000 Metal–Organic Framework

Abstract

Mononuclear and dinuclear copper species were synthesized at the nodes of an NU-1000 metal–organic framework (MOF) via cation exchange and subsequent oxidation at 200 °C in oxygen. Copper-exchanged MOFs are active for selectively converting methane to methanol at 150–200 °C. At 150 °C and 1 bar methane, approximately a third of the copper centers are involved in converting methane to methanol. Methanol productivity increased by 3–4-fold and selectivity increased from 70% to 90% by increasing the methane pressure from 1 to 40 bar. Density functional theory showed that reaction pathways on various copper sites are able to convert methane to methanol, the copper oxyl sites with much lower free energies of activation. Combining studies of the stoichiometric activity with characterization by in situ X-ray absorption spectroscopy and density functional theory, we conclude that dehydrated dinuclear copper oxyl sites formed after activation at 200 °C are responsible for the activity.

Copper-zirconia interfaces in UiO-66 enable selective catalytic hydrogenation of CO2 to methanol

“…To overcome this limitation, we exchanged Cu 2+ cations 14 for protons at under-coordinated Zr 6 O 8 nodes of UiO-66 (Supplementary Fig. 1c , route c) 15 that upon reduction at mild temperatures form metallic Cu particles, while not breaking a large fraction of the Cu–O–Zr bonds. By varying the loading and the reduction procedure, single Cu δ+ atoms and Cu particles not in contact with the node were synthesized also.…”

Sub‐3 nm Ultrafine Cu2O for Visible Light Driven Nitrogen Fixation

“…Cu K‐edge X‐ray absorption near‐edge spectroscopy (XANES) was used to examine the local structure of Cu atoms in the ultrafine Cu 2 O and bulk Cu 2 O reference samples (Figure 2 d and S7). The pre‐edge feature at around 8983.8 eV was assigned to a 1s→4p transition of a Cu I species, with the intensity of this spectral feature increasing in the order u‐Cu 2 O‐0.01M‐2h < u‐Cu 2 O‐0.05M‐2h < u‐Cu 2 O‐0.5M‐2h [27] . The amounts of ultrafine Cu 2 O loaded were further determined by inductively coupled plasma tests on the basis of “coordinating etching” strategy (see Table S1).…”

Bioinspired chemistry at MOF secondary building units

“…In an alternative strategy, Lercher and co-workers deposited Cu(II) ions onto the zirconium SBU of NU-1000. 44,45 The modi-ed MOFs outperform the unmodied ones in methane oxidation (Table 1). Activation occurs by exposure to 1 atm of O 2 followed by 1-40 bar methane at 150-200 C for 0.5 to 3 hours.…”