Paradoxically, one of the most widely and successfully tested metal−organic framework (MOF)-based catalysts, i.e., the Fe-BTC material commercialized as Basolite F300, entails a certain "mystery": Its structure is unknown and only an indirect and complex preparation method has been reported. This work describes an easy preparation method of a Basolite F300-like material. Furthermore, this synthesis procedure is carried out under environmentally and economically sustainable conditions: at room temperature, in a few minutes and using water as the unique solvent. Several characterization techniques indicate that both commercial and lab-made Fe-BTC materials are very much similar in so many physicochemical properties. However, the herein reported Fe-BTC possesses better textural properties, especially regarding the external surface area. Both Fe-BTC materials catalyze the oxidation of cyclohexene with very similar selectivity. However, the sample prepared in the laboratory gives a notably higher conversion, which was attributed to its external surface area. Iron leaching, if any, was negligible, and no significant structural transformation was detected. Finally, this paper also gives valuable structural information about the semiamorphous Fe-BTC: it exclusively contains the smallest mesocages of MIL-100(Fe), which provides an important input for interpreting the role of these Fe-BTC materials in any application demanding high porosity.
In some aspects, the potential of metal–organic framework (MOF) materials as heterogeneous catalysts has been realized, at least in an academic context. However, one of their most promising catalytic properties, that is, the presence of open metal sites, is far from understood properly. In this work, a series of M–MOF‐74 (M=Mn, Co, Ni, Cu, Zn) materials, prepared under sustainable conditions, was tested systematically in the oxidation of cyclohexene, which can proceed by either radical or epoxidation routes. Under the optimized reaction conditions, the radical route is spontaneous to some extent and it is enhanced in the presence of any M–MOF‐74 that has a metal with a redox character but not Zn. However, the epoxidation of cyclohexene is also promoted by a redox catalyst in such a way that the conversion correlates qualitatively with the redox potential of the metal. Thus, for the first time, a chemical property of M is correlated with the catalytic activity of the M–MOF‐74 family.
The dynamic behavior of a CuO/ZnO/Ga2O3 catalyst under Methanol Steam Reforming (MSR) reaction conditions promoted by a high dispersion of the copper nanoparticles and defect sites of a non-stoichiometric ZnGa2O4 spinel phase has been observed, where structural changes taking place in the initial state of the reaction determine the final state of the catalyst in stationary reaction conditions. Mass Spectrometry (MS) studies under transient conditions coupled to X-Ray Photoelectron Spectroscopy (XPS) have shown copper oxidation to Cu + in the initial state of the reaction (TOS = 4 min), followed by a fast reduction of the outer shell to Cu 0 , while keeping dissolved oxygen species in the inner layers of the nanoparticle. The presence of this subsurface oxygen impairs a positive charge to the uppermost surface copper species, i.e.Cu δ+ , which undoubtedly plays an important role on the MSR catalytic activity. The detection of these features, unperceived by conventional spectroscopic and catalytic studies, has only been possible by combining synchrotron NAP-XPS studies with transient studies performed in a low volume catalytic reactor connected to MS and linked with Raman and laboratory scale XPS studies.
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