Mixed-Metal Strategy on Metal–Organic Frameworks (MOFs) for Functionalities Expansion: Co Substitution Induces Aerobic Oxidation of Cyclohexene over Inactive Ni-MOF-74

Abstract

Different amounts of Co-substituted Ni-MOF-74 have been prepared via a post-synthetic metal exchange. Inductively coupled plasma mass spectrometry, powder X-ray diffraction (XRD), N2 adsorption/desorption, and extended X-ray absorption fine structure (EXAFS) analyses indicated the successful metathesis between Co and Ni in Ni-MOF-74 to form the solid-solution-like mixed-metal Co/Ni-MOF-74. It was found that introduction of active Co into the Ni-MOF-74 framework enabled the inert Ni-MOF-74 to show activity for cyclohexene oxidation. Since Co was favorably substituted at positions more accessible to the substrate, the mixed-metal Co/Ni-MOF-74 showed superior catalytic performance, compared with pure Co-MOF-74 containing a similar amount of Co. This study provides a facile method to develop solid-solution-like MOFs for heterogeneous catalysis and highlights the great potential of this mixed-metal strategy in the development of MOFs with specific endowed functionalities.

Controlled Pyrolysis of Ni‐MOF‐74 as a Promising Precursor for the Creation of Highly Active Ni Nanocatalysts in Size‐Selective Hydrogenation

“…Figure shows the Ni K‐edge X‐ray absorption near‐edge structure (XANES) and Fourier transformation of the extended X‐ray absorption fine structure (FT‐EXAFS) spectra of Ni‐MOF‐74‐T with reference samples. In the XANES spectra, the shape of Ni‐MOF‐74 before heat treatment was similar to that of NiO and Ni(NO 3 ) 2 , indicating Ni species in the Ni‐MOF‐74 network were present as Ni 2+ ions . The FT‐EXAFS spectrum for Ni‐MOF‐74 showed a strong absorption peak at around 1.7 Å, which was derived from the Ni−O bonds in the Ni cluster, and a second peak at around 2.7 Å attributed to neighboring Ni atoms (Ni‐O‐Ni bonds) .…”

“…Ni‐MOF‐74 was prepared using the following procedure . Ni(NO 3 ) 2 ⋅ 6 H 2 O (4.756 g) and 2,5‐dihydroxyterephthalic acid (0.956 g) were added into of a mixture of water, ethanol and DMF (400 mL with a molar ratio of 1:1:1).…”

Synthetic Strategies and Structural Arrangements of Isoreticular Mixed‐Component Metal–Organic Frameworks

“…However, often the size difference of the incorporated metals is rather small and therefore significant shifts of the corresponding reflections are difficult to observe with standard XRD setups. However, by using high‐resolution XRD measurements valuable information could be obtained for certain systems …”

Tandem magnetization and post‐synthetic metal ion exchange of metal–organic framework: Synthesis, characterization and catalytic study

“…The engineering of MM‐MOFs can lead to new frameworks with novel or multiple functions improving catalytic or gas sorption performance. Previous studies have shown the properties of several synthesized MM‐MOFs …”

“…Mixed‐metal MOFs were found to be potential heterogeneous catalysts with better catalytic performance compared with the analogous single‐metal MOFs. This superior performance is due to bi‐ and multi‐functional active catalytic sites that can promote reactions that require more than one type of site . For instance, NH 2 ‐UiO‐66(Zr/Ti) showed enhanced photocatalytic activity under visible light .…”