Efficient reversible oxygen electrodes for both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) are vitally important for various energy conversion devices, such as regenerative fuel cells and metal-air batteries. However, realization of such electrodes is impeded by insufficient activity and instability of electrocatalysts for both water splitting and oxygen reduction. We report highly active bifunctional electrocatalysts for oxygen electrodes comprising core-shell Co@Co3O4 nanoparticles embedded in CNT-grafted N-doped carbon-polyhedra obtained by the pyrolysis of cobalt metal-organic framework (ZIF-67) in a reductive H2 atmosphere and subsequent controlled oxidative calcination. The catalysts afford 0.85 V reversible overvoltage in 0.1 m KOH, surpassing Pt/C, IrO2 , and RuO2 and thus ranking them among one of the best non-precious-metal electrocatalysts for reversible oxygen electrodes.

Superhydrophobic/superoleophilic composites HFGO@ZIF-8 have been prepared from highly fluorinated graphene oxide (HFGO) and the nanocrystalline zeolite imidazole framework ZIF-8. The structure-directing and coordination-modulating properties of HFGO allow for the selective nucleation of ZIF-8 nanoparticles at the graphene surface oxygen functionalities. This results in localized nucleation and size-controlled ZIF-8 nanocrystals intercalated in between HFGO layers. The composite microstructure features fluoride groups bonded at the graphene. Self-assembly of a unique micro-mesoporous architecture is achieved, where the micropores originate from ZIF-8 nanocrystals, while the functionalized mesopores arise from randomly organized HFGO layers separated by ZIF-8 nanopillars. The hybrid material displays an exceptional high water contact angle of 162° and low oil contact angle of 0° and thus reveals very high sorption selectivity, fast kinetics, and good absorbencies for nonpolar/polar organic solvents and oils from water. Accordingly, Sponge@HFGO@ZIF-8 composites are successfully utilized for oil-water separation.

The fabrication of metal nanoparticles (NP) in porous host matrices, especially metal-organic frameworks (MOFs) has become of great interest in recent years, due to the broad field of applications. In this article we summarize the progress in the field of NP@MOF materials and illustrate the different preparation methods as well as suitable characterisation techniques. Furthermore, practical applications in the fields of hydrogen storage and heterogeneous catalysis are briefly discussed.

Titania exhibits unique photo-physical and -chemical properties and can be used for potential applications in the field of photocatalysis. The control of TiO2 in terms of phase, shape, morphology, and especially nano-scale synthesis of TiO2 particles still remains a challenge. Ti-containing metal-organic frameworks (MOFs), such as MIL-125, can be used as sacrificial precursors to obtain TiO2 materials with diverse phase compositions, morphologies, sizes and surface areas. MIL-125 is composed of Ti/O clusters as the secondary building units (SBUs) bridged by 1,4-benzene-dicarboxylate (bdc). In this study, pre-formed and surfactant stabilized gold nanoparticles (GNPs) were deposited onto the surface of amino functionalized NH2-MIL-125 during solvothermal synthesis. Targeted gold/titania nano composites, GNP/TiO2, were fabricated through the pyrolysis of GNP/NH2-MIL-125 nanocrystals. The modification of TiO2 with GNPs significantly increased the photocatalytic activity of the MOF derived TiO2 material for the reduction of CO2 to CH4 as compared to TiO2 reference samples such as P-25 and Aurolite (Au/TiO2). The new materials GNP/TiO2 and TiO2 derived by the MOF precursor route were thoroughly characterized by PXRD, FTIR and RAMAN, TEM and N2 adsorption studies.

Solvent mixture controlled rapid room temperature syntheses for facile access to uniform zeolitic-imidazolate framework nanocrystals (ZIF-7, ZIF-65-Zn and ZIF-71) are reported. ZIF thin film devices for sensing volatile organic chemicals were fabricated by dip-coating nano-ZIF (80-130 nm) suspensions.

Metal-organic frameworks (MOFs) feature a great possibility for a broad spectrum of applications. Hollow MOF structures with tunable porosity and multifunctionality at the nanoscale with beneficial properties are desired as hosts for catalytically active species. Herein, we demonstrate the formation of well-defined hollow Zn/Co-based zeolitic imidazolate frameworks (ZIFs) by use of epitaxial growth of Zn-MOF (ZIF-8) on preformed Co-MOF (ZIF-67) nanocrystals that involve in situ self-sacrifice/excavation of the Co-MOF. Moreover, any type of metal nanoparticles can be accommodated in Zn/Co-ZIF shells to generate yolk-shell metal@ZIF structures. Transmission electron microscopy and tomography studies revealed the inclusion of these nanoparticles within hollow Zn/Co-ZIF with dominance of the Zn-MOF as shell. Our findings lead to a generalization of such hollow systems that are working effectively to other types of ZIFs.

Zinc–zinc interactions on nickel and palladium centers are highly dependent on the co-ligands. These dependencies are also found for the formation of dihydrogen vs. dihydride complexes and underline the analogy [Zn2Cp*2] ↔ H2.

Host‐guest inclusion properties of UiO‐66 and UiO‐67 metal‐organic frameworks have been studied using ferrocene (FeCp2) as probe molecule. According to variable‐temperature solid‐state 1H and 13C CP‐MAS‐NMR, two different environments exist for adsorbed FeCp2 inside UiO‐66 and UiO‐67, which have been assigned to octahedral and tetrahedral cavities. At room temperature, a rapid exchange between these two adsorption sites occurs in UiO‐67, while at –80 °C the intracrystalline traffic of FeCp2 through the triangular windows is largely hindered. In UiO‐66, FeCp2 diffusion is already impeded at room temperature, in agreement with the smaller pore windows. Palladium nanoparticles (Pd NPs) encapsulated inside UiO‐66 and UiO‐67 have been prepared by chemical vapor infiltration of (allyl)Pd(Cp) followed by UV light irradiation. Infiltration must be carried out at low temperature (–10 °C) to avoid uncontrolled decomposition of the organometallic precursor and formation of Pd NPs at the external surface of the MOF. The resulting Pd‐MOFs are shape selective catalysts, as shown for the hydrogenation of carbonyl compounds with different steric hindrance.