Diana Julião

Influence of a porous MOF support on the catalytic performance of Eu-polyoxometalate based materials: desulfurization of a model diesel

An aluminum 2-aminoterephthalate based metal–organic framework (MOF) material was applied for the first time to prepare highly efficient heterogeneous catalysts in desulfurization processes. Sandwich-type [Eu(PW11O39)2]11− polyoxometalate (POM) was supported on Al(III) and Cr(III) MIL-type MOFs, NH2-MIL-53(Al) and MIL-101(Cr), and extensive characterization confirmed the incorporation of the POM on the two supports. The catalytic performance of the two composite materials, POM/MIL(Al) and POM/MIL(Cr), was evaluated in the oxidative desulfurization (ODS) of a model fuel containing some of the most common refractory sulfur compounds in diesel. Both composite materials have shown to be active and robust heterogeneous catalysts for the efficient removal of the sulfur-containing compounds from the model diesel, and the influence of the solid support on the catalytic performance of the active species was further assessed. The POM/MIL(Al) revealed notable catalytic performance, since complete desulfurization was obtained after 2 h of reaction. Furthermore, this remarkable heterogeneous catalyst revealed to be stable and recyclable for various catalytic cycles.

Cobalt aluminate nanoparticles supported on MIL-101 structure: catalytic performance investigation

The first catalytic active composites based on CoAl2O4 nanoparticles with different size (5.5 and 2.5 nm) were successfully prepared using a simple methodology of incorporation into MIL-101(Cr) framework, CoAl-x@MIL(Cr). Characterization of CoAl-x@MIL(Cr) composites by elemental analysis, vibrational spectroscopy (FT-IR and FT-Raman), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX) confirmed the successful preparation and stability of the support structure after nanoparticle immobilization. A remarkable catalytic performance was found for thioanisole oxidation under sustainable conditions (95% of conversion after 30 min of reaction) and the catalytic application of the most active composite was extended to styrene oxidation. Higher catalytic performance was achieved for the composite prepared with larger CoAl2O4 nanoparticles. The recyclability and the stability of composites after catalytic use were investigated. For the CoAl-x@MIL(Cr) catalytic systems, the loading parameter instead of the nanoparticle size seemed to have a pronounced influence in the heterogeneous catalytic performance. The confinement effect promoted by MIL-101(Cr) cavities associated to the higher number of catalytic active centers (CoAl2O4) is clearly more important than the size of the catalytic nanoparticles used.

Improved catalytic performance of porous metal–organic frameworks for the ring opening of styrene oxide

An emerging strategy to improve the performance of porous metal–organic framework (MOF) materials as heterogeneous catalysts is reported. The incorporation of the iron-substituted polyoxometalate (POM) TBA4[PW11Fe(H2O)O39] (PW11Fe) in porous MOF NH2-MIL-101(Fe), leading to a novel composite based MOF material, PW11Fe@NH2-MIL-101(Fe), was revealed to be a significant approach to increase the efficiency of the MOF material as a regioselective catalyst for the ring opening of styrene oxide with aniline. The conversion after 1 h of reaction using NH2-MIL-101(Fe) is 22% and increases to 100% when PW11Fe@NH2-MIL-101(Fe) is employed as catalyst. It is noteworthy that the catalytic performance of this composite material is also considerably better than that obtained with the respective physical mixture under similar conditions. Furthermore, PW11Fe@NH2-MIL-101(Fe) revealed to be a remarkable selective heterogeneous catalyst for the studied reaction (100% selectivity to the 2-phenylamino-2-phenylethanol isomer) with significant robustness and recyclability.