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We report a highly selective (100 %) epoxidation of α‐pinene and R‐carvone using an oxygen atom transfer (OAT) reaction facilitated by a dioxo‐Mo complex (Mo(VI)O2Cl2Ln) incorporated into the ligand 5,5'‐dicarboxylate‐2,2'‐bipyridine (bpydc) within a Metal‐Organic Framework (MOF) type UiO‐67. Photo‐stimulated (350 nm) OAT reaction was carried out with oxygen molecular used as the oxidant for 10 h. UiO‐67 was synthesized with a mixture of the ligands 2,2′‐biphenyl‐5,5′‐dicarboxylate (bpdc) and 2,2‐bipyridine‐5,5‐dicarboxylate (bpydc) in different molar ratios (67 : 33, 50 : 50, 70 : 30, 0 : 100 bpdc : bpydc) to promote a higher presence of catalytic sites, i. e., the dioxo‐Mo complex units. Furthermore, a post‐synthetic exchange of Zr for Ti, between 64 : 36 to 78 : 22 Ti : Zr molar ratio, was performed to improve the optical properties of the MOF and promote the photoinduced OAT reaction. The Catalytic system was characterized by FTIR, XRD, 1H NMR, XPS, TGA, N2 adsorption/desorption and UV‐Vis‐DR. The amount of the epoxide monoterpene is proportional to the number of the dioxomolybdenum(VI) units (MoO2) incorporated in the UiO‐67 (Zr/Ti), and the OAT reaction selectivity is due to the absence of the oxygen radicals in the medium of reaction. Besides, The Mo complex exhibited excellent stability after five cycles of use. [ABSTRACT FROM AUTHOR]

Zr-MOFs are characterized by their high thermal and chemical stability which may facilitate their application in heterogeneous catalysis. However, these applications could be restricted if large reactants exceed the MOF pore sizes leading to unavailable surface areas. In this work, we study the effect of acetic acid concentration, used as a modulator, on the formation of micro/mesoporous materials. This inclusion of a modulator during synthesis and its removal by an activation process generate materials with missing linker defects. We show that an increase in the concentration of modulator leads to an improvement of the calculated apparent surface area and to a modification of the MOF-808 pore structure by producing mesopores at the expense of micropores. Furthermore, we perform a post-synthetic modification (PSM) of MOF-808. We observe the expected sulfation of the zirconium oxo-cluster but also the sulfonation of the organic ligand. Also, we find that only the families of mesopores and the larger micropores are interconnected within the material, and the ultramicropores seem to be isolated from the porous structure. The PSM process led to the addition of Lewis and Brønsted acid sites to MOF-808. Experimental results are complemented by theoretical calculations using density functional theory and ab initio molecular dynamics simulations. The rationalization of the effect of synthesis conditions and the post-synthetic sulfation process on the final properties presented in this paper can serve as a basis for engineering of defects towards the synthesis of solid acid catalysts from MOF-808. [ABSTRACT FROM AUTHOR]

Due to their thermal and chemical stability, zirconium-based metal–organic frameworks (Zr-MOFs) have been extensively studied in the literature. However, many details of the influence of preparation conditions are still unclear. Most papers tend to use one type of metallic precursor for synthesizing Zr-MOFs such as MOF-808. Therefore, as far as we know, a systematic analysis of the effect of zirconium precursors on the properties of MOF-808 has not been conducted. In this work, three different metallic precursors were employed, namely, zirconium chloride, zirconyl chloride, and zirconyl nitrate for synthesizing MOF-808 while keeping all other synthesis conditions constant. The results of the study indicated the following: (i) the nature of the zirconium precursor impacts the crystalline and porous structure of MOF-808. Particularly, the presence of structural water in the precursors seems to cause a detriment to these properties which resulted in an increase of the relative percentage of amorphicity of the materials as well as the formation of disorganized mesopores. (ii) In contrast to (i), the surface properties of the materials and their thermal stability under an air atmosphere were not altered by the use of the different precursors. All the materials exhibited a surface populated by free and uncoordinated carboxylates as well as inorganic zirconium structures corresponding to uncoordinated oxo-clusters. The ensemble of these findings contributes to a better understanding of the features that make MOFs interesting for diverse applications. Particularly, studies on defect engineering may benefit from the insight into surface chemistry provided in this contribution. [ABSTRACT FROM AUTHOR]

This article, published in the European Journal of Inorganic Chemistry, discusses the use of a dioxo-molybdenum complex anchored to a metal-organic framework (MOF) called UiO-67 (Zr) for the selective oxidation of a monoterpene to an epoxide. The researchers implemented a post-synthetic exchange process to modify the photochemical properties of the MOF. The photo-induced oxygen atom transfer (OAT) reaction occurs through the interaction of a Mo(IV) species with molecular oxygen under UV-vis light, resulting in the regeneration of the catalytically active unit. The article provides more detailed information on this research. [Extracted from the article]

• The incorporation of an oxo-diperoxo MoVI complex in a MIL-125-NH2(Ti) was studied. • The resulting MOFs were isotypic to the MIL-125-NH2 with some textural differences. • In the absence of O2, the catalysts could transfer 4 O atoms to 4 olefin molecules. • The reduced Mo-unit was re-oxidized to the oxo-diperoxo when O2 bubbling was applied. • High catalytic performance (UV light+O2) was achieved in the epoxidation of α-pinene. An oxo-diperoxo molybdenum (VI) complex was anchored on a MIL-125-NH 2 Metal-Organic Framework (MOF), and its Oxygen Atom Transfer (OAT) catalytic performance in the photo-epoxidation of α-pinene was evaluated. MIL-125-NH 2 was modified with salicylaldehyde and pyridine-2-aldehyde by a post-synthetic approach to produce Schiff base ligands. Then, a MoVI complex was incorporated into the resulting MOFs. Bulk and surface characterization evidenced the incorporation of the Shiff base ligands and the MoO(O 2) 2 complex inside the Ti-MOF by studying the effect on the properties of each post-synthetic step. The final MOFs effectively achieved the transfer of 4 oxygen atoms to 4 olefin molecules during the irradiation but without the presence of any oxidant. The complete reoxidation of the oxo-Mo-center with O 2 was reached since it presented the same catalytic activity after the oxygenation cycle. Also, α-pinene oxide resulted as the main product of photoinduced OAT long-term reaction, showing high performance in the epoxidation of olefins. [Display omitted] [ABSTRACT FROM AUTHOR]

The use of Titanium-based Metal-Organic Frameworks (MOFs) as substitutes for titanium dioxide in photocatalytic applications is a recent topic of study. A promising approach is to perform a titanium exchange within a zirconium-based MOF to build a material that combines the properties of the two metals, high thermal stability, and photoactivity. In this work, a novel Zr/Ti MOF that incorporated a dioxo-molybdenum (VI) complex was successfully prepared using two post-synthetic steps. First, a molybdenum complex was anchored to a bipyridine-dicarboxylate linker of a UiO-67 type MOF. Second, a Ti4+ ion exchange for Zr4+ at the zirconium MOF nodes was performed. The as-prepared samples were characterized by PXRD, TGA, FT-IR, N 2 adsorption, XPS, SEM and UV–vis in diffuse reflectance mode. The introduction of titanium changed the optical properties of UiO-67 adding advantages through the TiO 2 moieties attached to its structure. This was attributed to the metal exchange and the formation of oxo-bridged hetero-Zr-Ti clusters with some loss of crystallinity. Additionally, the addressed surface characterization showed that dioxo-molybdenum (VI) and titanium were incorporated into the structure of Zr-MOF with a small decrease in the surface BET area. Image 1 • The incorporation of a molybdenum complex in a titanium-doped Zr-MOF was studied. • The resulting MOFs were isotypic to the UiO-67 with small structural differences. • Titanium and Mo-complex incorporation in a UiO-67 MOF generated optical changes. • A rigorous analysis of the surface chemistry of the resulting MOFs was performed. [ABSTRACT FROM AUTHOR]