Nanocatalysts Derived from Copper Phyllosilicate for Selective Hydrogenation of Quinoline

1,2,3,4-Tetrahydroquinoline (py-THQ) is a vital intermediate that is used in the production of medicines, agricultural chemicals, and other fine chemicals and is synthesized through the selective hydrogenation of quinoline. In this work, copper phyllosilicate catalysts were prepared by four different synthesis methods: deposition precipitation, ammonia evaporation, a urea-assisted gel method, and hydrothermal treatment. It was found that the different synthesis strategies led to different actual loadings of copper in the precursors. The optimal catalyst showed a py-THQ selectivity of 99.9% at a full conversion of quinoline in ethanol at 100 °C and 3.0 MPa H2 for 2 h. The remarkable enhancement of the performance may be attributed to the small particle size, the coexistence of Cu0 and Cu+, and the strong interaction of copper phyllosilicate by the deposition precipitation preparation method. The characterization results showed that Cu0 and Cu+ were generated during the restoration process and were derived from CuO and layered copper phyllosilicates, respectively. Additionally, the ratio of Cu+/(Cu+ + Cu0) changed with the reduction temperature. The strategy of the catalyst design and synthesis developed in this work has potential applications in other nitrogen heterocyclic hydrogenation reactions

Ion-Specific Effects on Hydrogen Bond Network at a Submicropore Confined Liquid-Vacuum Interface: An <i>in Situ</i> Liquid ToF-SIMS Study

The hydrogen bond (HB), one of the essential properties of water, tends to link water molecules to form dynamic water clusters. Extrinsic ions could change the size distribution of water clusters by influencing HBs. But the mechanism, especially the influence range of ions on HBs, is still in dispute due to limitation of analytical methods. Herein, we use in situ liquid ToF-SIMS analysis combined with density functional theory calculation to study the influence of different halide anions on HBs at a submicropore confined liquid–vacuum interface. Our experimental results demonstrated that anions show synchronous local and long-range effects on HBs. Specifically, the larger the anion is, the greater degree the long-range HB network and the local hydration number of anions are influenced. More importantly, we found that the long-range effect on the HB network is influenced by nuclear quantum effects, whereas the local effect on water molecules in the first hydration shell is not

Selective Hydrodeoxygenation of Furfural to 2‑Methylfuran over Silica-Supported MoP Catalysts under Mild Conditions

In the catalytic conversion of biomass-derived furfural to 2-methylfuran, a concerted combination of hydrogenation and hydrogenolysis is required. Highly dispersed MoP catalysts supported on SiO2 were prepared by incipient impregnation with the aid of citric acid and subsequent temperature-programmed hydrogen reduction. The prepared MoP/SiO2 exhibited a markedly high performance in the selective hydrodeoxygenation of furfural to 2-methylfuran. A full conversion of furfural with 96.3% selectivity to 2-methylfuran under mild reaction conditions (120 °C, 1.0 MPa, WHSV: 0.3 h–1) was obtained with over 20% MoP/SiO2 in a continuous fixed bed reactor. The oxophilicity of Mo species and surface acidity of MoP might enhance the adsorption of furfural and the subsequent cleavage of the C–O bond of the intermediate furfuryl alcohol, leading to considerably high selectivity to 2-methylfuran. The complexion of Mo species with citric acid improved the dispersion of MoP particles due to the controllable decomposition of the complex in the course of preparation. Although the activity of MoP/SiO2 decreased gradually with the reaction time in 50 h, it could be restored by in situ hydrogen reduction

Efficient Ni₂P/SiO₂ Catalysts with Enhanced Performance for the Hydrogenation of 4,6-Dimethyldibenzothiophene and Phenanthrene

Highly dispersed Ni2P catalysts (Ni2P/SiO2-DPx) were prepared by reducing the passivation-free precursors, which were obtained through the phosphidation of nickel phyllosilicate with sodium hypophosphite. The strong metal–support interaction of nickel phyllosilicate and the mild phosphidation conditions prevented the agglomeration of Ni particles and resulted in a smaller Ni2P particle size. The superior catalytic performance of the as-prepared Ni2P/SiO2-DP catalysts was evaluated in hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene and the hydrogenation of phenanthrene, in comparison with Ni2P/SiO2-IM and CoMoS/γ-Al2O3 prepared from a conventional incipient wetness impregnation method. The passivation-free Ni-P/SiO2-DPx precursors showed great storage stability, and Ni2P/SiO2-DP derived from the stored Ni-P/SiO2-DP precursors exhibited negligible loss of HDS activity. This method provides a potential preparation strategy for the industrial applications of transition metal phosphides without the temperature-programmed reduction and the subsequent passivation process

Highly Reproducible Ag NPs/CNT-Intercalated GO Membranes for Enrichment and SERS Detection of Antibiotics

The increasing pollution of aquatic environments by antibiotics makes it necessary to develop efficient enrichment and sensitive detection methods for environmental antibiotics monitoring. In this work, silver nanoparticles and carbon nanotube-intercalated graphene oxide laminar membranes (Ag NPs/CNT-GO membranes) were successfully prepared for enrichment and surface-enhanced Raman scattering (SERS) detection of antibiotics. The prepared Ag NPs/CNT-GO membranes exhibited a high enrichment ability because of the π–π stacking and electrostatic interactions of GO toward antibiotic molecules, which enhanced the sensitivity of SERS measurements and enabled the antibiotics to be determined at sub-nM concentrations. In addition, the nanochannels created by the intercalation of CNTs into GO layers resulted in an 8-fold enhancement in the water permeance of Ag NPs/CNT-GO membranes compared to that of pure GO membranes. More importantly, the Ag NPs/CNT-GO membranes exhibited high reproducibility and long-term stability. The spot-to-spot variation in SERS intensity was less than 15%, and the SERS performance was maintained for at least 70 days. The Ag NPs/CNT-GO membranes were also used for SERS detection of antibiotics in real samples; the results showed that the characteristic peaks of antibiotics were obviously recognizable. Thus, the sensitive SERS detection of antibiotics based on Ag NPs/CNT-GO offers great potential for practical applications in environmental analysis

A Green Alternative for the Direct Aerobic Iodination of Arenes Using Molecular Iodine and a POM@MOF Catalyst

Iodoarenes are important precursors for fine chemicals and pharmaceuticals. The direct iodination of arenes using molecular iodine (I2) has emerged as an attractive green synthesis method. Most of the direct iodination protocols are still homogeneous systems that require harsh conditions and use or produce toxic products. We report a new heterogeneous catalytic route for the direct aerobic iodination of arenes under mild conditions using a PMoV2 polyoxometalate (POM) embedded in the metal–organic framework (MOF) MIL-101 (PMoV2@MIL-101). The catalyst shows full yield for the conversion of mesitylene to 2-iodomesitylene at a rate that is similar to the homogeneous POM system. Moreover, the catalyst is applicable for a wide range of substrates in an oxygen atmosphere without using any co-catalysts or sacrificial agents. To the best of our knowledge, this is the first report on designing a sustainable and green MOF-based heterogeneous catalytic system for the direct iodination reaction using molecular oxygen and iodine

Lithium-Based 3D Coordination Polymer with Hydrophilic Structure for Sensing of Solvent Molecules

A lithium-based coordination polymer is synthesized from 1,3-benzene dicarboxylate acid with lithium perchlorate through a solvothermal way. The complex features a 3D hydrophilic structure. The adsorption of water and organic solvents on this coordination polymer was investigated in situ by quartz crystal microbalance (QCM), which indicated that this framework is highly sensitive to water and methanol

Lithium-Based 3D Coordination Polymer with Hydrophilic Structure for Sensing of Solvent Molecules

A lithium-based coordination polymer is synthesized from 1,3-benzene dicarboxylate acid with lithium perchlorate through a solvothermal way. The complex features a 3D hydrophilic structure. The adsorption of water and organic solvents on this coordination polymer was investigated in situ by quartz crystal microbalance (QCM), which indicated that this framework is highly sensitive to water and methanol

Lithium-Based 3D Coordination Polymer with Hydrophilic Structure for Sensing of Solvent Molecules

A lithium-based coordination polymer is synthesized from 1,3-benzene dicarboxylate acid with lithium perchlorate through a solvothermal way. The complex features a 3D hydrophilic structure. The adsorption of water and organic solvents on this coordination polymer was investigated in situ by quartz crystal microbalance (QCM), which indicated that this framework is highly sensitive to water and methanol

Bipyridine-Based Nanosized Metal–Organic Framework with Tunable Luminescence by a Postmodification with Eu(III): An Experimental and Theoretical Study

A gallium 2,2′-bipyridine-5,5′-dicarboxylate metal–organic framework, Ga­(OH)­(bpydc), denoted as COMOC-4 (COMOC = Center for Ordered Materials, Organometallics and Catalysis, Ghent University) has been synthesized via solvothermal synthesis procedure. The structure has the topology of an aluminum 2,2′-bipyridine-5,5′-dicarboxylate – the so-called MOF-253. TEM and SEM micrographs show the COMOC-4 crystals are formed in nanoplates with uniform size of 30–50 nm. The UV–vis spectra of COMOC-4 in methanol solution show maximal electronic absorption at 307 nm. This results from linker to linker transitions as elucidated by time-dependent density functional theory simulations on the linker and COMOC-4 cluster models. When excited at 400 nm, COMOC-4 displays an emission band centered at 542 nm. Upon immersion in different solvents, the emission band for the framework is shifted in the range of 525–548 nm depending on the solvent. After incorporating Eu³⁺ cations, the emission band of the framework is shifted to even shorter wavelengths (505 nm). By varying the excitation wavelengths from 250 to 400 nm, we can fine-tune the emission from red to yellowish green in the CIE diagram. The luminescence behavior of Eu³⁺ cations is well preserved and the solid-state luminescence lifetimes of τ₁ = 45 μs (35.4%) and τ₂ = 162 μs (64.6%) are observed