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.
An insoluble solid support of N−heterocyclic imidazolium‐functionalized cage‐like silsesquioxane (SQ); Bim‐SQ, was synthesized by nucleophilic substitution of octakis(3‐chloropropyl)octasilsesquioxane with an excess bis‐(imidazol‐1‐yl)methane and investigated as a new organic‐inorganic hybrid support. In the presence of Bim‐SQ, Pd(II) from [PdCl4]2− can be stabilized via both electrostatic interactions and imidazole‐N‐coordination, giving an amorphous material of Pd(II)@Bim‐SQ. Subsequent in situ reduction of Pd(II)@Bim‐SQ during Suzuki−Miyaura cross‐coupling reactions afforded monodispersed Pd nanoparticles (2.33 ± 1.50 nm) stablized on Bim‐SQ support, PdNp@Bim‐SQ with Pd loading up to 14% w/w. Catalytic studies revealed that the pre‐catalyst Pd(II)@Bim‐SQ was active heterogeneous catalyst for Suzuki−Miyaura cross‐coupling reactions, having the maximum TOFs of 5400 h−1 under mild conditions and in aqueous ethanol medium. Furthermore, PdNp@Bim‐SQ was also shown to be an efficient catalyst for Heck reactions. Simple catalyst recovery and reusability of PdNp@Bim‐SQ for at least 5 catalytic cycles without loss of activity were also demonstrated.
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.
Most metal–organic frameworks (MOFs) lack charge mobility, which is crucial for realizing their use in optoelectronic applications. This work proposes the design of a MOF using triarylamine‐based ligands (Zr‐NBP) as the lone pair electron spacer to enhance the hole mobility in the MOF while maintaining its luminescent properties. Zr‐NBP has strong fluorescence with a good hole mobility of 1.05×10−6 cm2 V−1 s−1, which is comparable to organic materials used in optoelectronic devices. We also employed a Zr‐NBP nanofilm in the pure phase as both a non‐doped emissive layer and a hole‐transporting layer within organic light‐emitting diodes (OLEDs). The obtained OLED device produced a bright green light with a low turn‐on voltage of 3.9 V. This work presents an advance in developing the electronic properties of MOFs by modifying the chemical properties of its building blocks, and will likely inspire further design of MOF materials as active layers in optoelectronic devices.
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