U-Hwang Lee

Catalytic transfer hydrogenation of ethyl levulinate to γ-valerolactone over zirconium-based metal–organic frameworks

A series of highly crystalline, porous, zirconium-based metal–organic frameworks (Zr-MOFs) with different ligand functionalities and porosities were applied for catalytic transfer hydrogenation of ethyl levulinate (EL) to form γ-valerolactone (GVL), using isopropanol as a hydrogen donor. The roles of the ligand functionality and the metal center of the Zr-MOFs were identified and reaction parameters optimized, for selective production of GVL. The maximum yield of GVL (up to 92.7%) was achieved in 2 h at 200 °C with UiO-66(Zr). Interestingly, zirconium trimesate (MOF-808) emerged as the most suitable candidate, with the highest GVL formation rate (94.4 μmol g−1 min−1) among the catalysts tested at 130 °C. It was also found to be effective in conversion of EL to GVL in an open system using the solvent refluxing method. Both the catalysts (UiO-66(Zr) and MOF-808) were recycled at least five times under their specified reaction conditions without a notable change in catalytic activity and product selectivity. Fresh and recycled catalysts were characterized in detail using X-ray powder diffraction (XRD), N2 adsorption–desorption, thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) in order to understand the stability and structural changes that occurred in the catalysts. Finally, a plausible reaction mechanism was presented on the basis of active sites present in catalysts confirmed by characterization results.

An integrated process for the production of 2,5-dimethylfuran from fructose

2,5-Dimethylfuran was successfully produced in 92% overall yield from fructose in 1-butanol through a combination of dehydration over Amberlyst-15 and hydrogenolysis over the Ru–Sn/ZnO catalyst. The environmental favorability of this process, and its unprecedented efficiency, makes it promising from both a green chemistry and an industrial perspective.

Novel amine-functionalized iron trimesates with enhanced peroxidase-like activity and their applications for the fluorescent assay of choline and acetylcholine

We herein describe novel amine-grafted metal-organic frameworks (MOFs) as a promising alternative to natural peroxidase enzyme and their applications for a fluorescent assay of choline (Cho) and acetylcholine (ACh). Among diverse amine-functionalized MOFs, N,N,N,N-tetramethyl-1,4-butanediamine (TMBDA)-functionalized MIL-100(Fe) (TMBDA-MIL-100(Fe)) exhibited the highest peroxidase activity by developing intense fluorescence from Amplex UltraRed (AUR) in the presence of H2O2, which was presumably due to the synergetic effect of the enhanced negative potential and precisely controlled molecular size of the grafted diamine. Based on the excellent peroxidase-like activity of TMBDA-MIL-100(Fe), choline and ACh were reliably determined down to 0.027 and 0.036µM, respectively. Furthermore, practical applicability of this strategy was successfully demonstrated by detecting choline and ACh in spiked samples of milk and serum, respectively. This work highlights the advantages of amine-grafted MOFs for the preparation of biomimetic catalysts, extending their scope to biosensor applications.

Size and morphological control of a metal–organic framework Cu-BTC by variation of solvent and modulator

AbstractnA metal–organic framework of copper 1,3,5-benzenetricarboxylate (Cu-BTC) has been synthesized using the microwave-assisted method, with different solvents. Synthesized compounds were washed repeatedly with a mixture of deionized water and ethanol to ensure the removal of impurities. Finally, purified samples were characterized using XRD and SEM to understand their morphological and structural features. The effect of solvent and modulator (dodecanoic acid) on the crystallinity and morphology of synthesized particles was investigated. The crystallinity depends on the dielectric constant and dielectric loss factor of the solvent used. The Cu-BTC crystals synthesized using ethylene glycol at low concentration [mole ratio of copper salt (1) to ethylene glycol (180)] were octahedral, but increasing the concentration [mole ratio of copper salt (1) to ethylene glycol (36)] changed the crystal morphology from octahedral to hexagonal. Interestingly, a dramatic change in the particle size and morphology was observed for Cu-BTC synthesized using ethylene glycol with coordination modulator.

Design of a heterogeneous catalytic process for the continuous and direct synthesis of lactide from lactic acid

We present a continuous one-step reaction pathway for optically pure lactide under atmospheric conditions based on a novel SnO2–SiO2 nanocomposite catalyst. The new heterogeneous catalytic system gave a record high lactide yield of 94% with almost 100% enantioselectivity and long-term stability (>2500 h) from L-lactic acid.

Shaping of porous metal–organic framework granules using mesoporous ρ-alumina as a binder

The shaping of metal–organic frameworks (MOFs) on a macroscopic level is a vibrant area in MOF research. For practical application of MOFs, the fine microcrystalline powder should be converted into a shaped body while preserving the powders intrinsic properties. In this study, we prepared millimetre-scale spheres of MIL-100(Fe), MIL-101(Cr), UiO-66(Zr), and UiO-66(Zr)_NH2 using the wet granulation method. The use of mesoporous ρ-alumina (MRA) as a binder resulted in well-shaped MOF bodies which retained their intrinsic properties after shaping. Furthermore, the performance of the MOF spheres was compared to that of compressed pellets in terms of NH3 adsorption using a breakthrough test, and CO2 and N2 adsorption performance was compared using adsorption isotherms at 298 K between the powder and spheres of MOFs for future industrial applications.