Abstract5‐hydroxylmethylfurfural (HMF) is a bio‐based chemical that can be prepared from natural abundant glucose by using combined Brønsted–Lewis acid catalysts. In this work, Al3+ catalytic site has been grafted on Brønsted metal–organic frameworks (MOFs) to enhance Brønsted–Lewis acidity of MOF catalysts for a one‐pot glucose‐to‐HMF transformation. The uniform porous structure of zirconium‐based MOFs allows the optimization of both acid strength and density of acid sites in MOF‐based catalysts by incorporating the desired amount of Al3+ catalytic sites at the organic linker. Al3+ sites generated via a post‐synthetic modification act as Lewis acid sites located adjacent to the Brønsted sulfonated sites of MOF structure. The local structure of the Al3+ sites incorporated in MOFs has been elucidated by X‐ray absorption near‐edge structure (XANES) combined with density functional theory (DFT) calculations. The cooperative effect from Brønsted and Lewis acids located in close proximity and the high acid density is demonstrated as an important factor to achieve high yield of HMF.
Zirconium clusters of UiO-66 have been hydroxylated with
NaOH to
generate strong binding sites for As(III) species in wastewater treatment.
Hydroxylated UiO-66 provides high adsorption capacity over a wide
range of pH from 1 to 10 with a maximum uptake of 204 mg g–1, which is significantly enhanced compared to those of pristine UiO-66,
acid-modulated UiO-66, and other adsorbents for use in a wide pH range
of treatment processes. The local structure of hydroxylated sites
and As(III) adsorption mechanism are determined by extended X-ray
absorption fine structure combined with density functional theory
calculations.
The structure of the melt state of one-dimensional (1D) coordination polymer crystal Cu(isopropylimidazolate) (melting temperature Tm =143 °C) was characterized by DSC, variable temperature PXRD, solid-state NMR, viscoelastic measurements, XAS,...
Extensive studies have been done on the modification of the organic linkers with different functional groups for ameliorating the properties of Zr-based metal-organic frameworks (MOFs). In contrast, little effort has been devoted to Zr MOF modification at the –OH group arising from the incomplete coordination of Zr with the organic linkers. We focused on covalently immobilizing redox-active iron to the –OH group in the node of a Zr-based MOF for selective oxidation of benzyl alcohol to benzaldehyde, which is an important reaction in organic synthesis, pharmaceutical, and industrial areas. In this work, iron acetylacetonate was incorporated into Zr6(μ3-O)4(μ3-OH)4(HCOO)6(1,3,5-benzenetricarboxylate)2 or MOF-808. The air-stable Fe-anchored MOF-808 (Fe-MOF-808) was subjected to screening for the selective oxidation of benzyl alcohol to benzaldehyde. Fe-MOF-808 showed enhanced conversion and selectivity to benzaldehyde as well as catalytically outperforming the pristine MOF-808 in the reaction. The prepared solid catalyst also displayed the robustness without the leaching of the active site during the reaction, along with at least four-time recyclability of use without significant deactivation.
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