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Tailoring the Linear and Second-Order Nonlinear Optical Responses of the Titanium-MIL-125 Metal-Organic Framework through Ligand Functionalization: A First Principles Study
摘要： Density functional theory calculations have been performed to investigate the linear and second order nonlinear optical (NLO) properties of titanium-based MIL-125 metal-organic frameworks in crystalline form, in which the 1,4-benzene-dicarboxylate (BDC) linkers are modified by introducing different functional groups or by extending BDC ligand to contain two (MIL-126) and three (MIL-127) benzene rings. Our results reveal that the functionalization of BDC linker tends to increase the dielectric constants and the magnitude of birefringence of MIL-125, especially for the aminated derivatives. Correspondingly, the incorporation of substituent group will improve the phase matching performance of MIL-125. As for the second harmonic generation (SHG) susceptibility, the SHG activity of the pristine MIL-125 is comparable to KDP, which can be attributed mostly to the contributions of TiO5(OH) octahedra. It is noted that after introducing substituent group into BDC linker, the organic part will have a remarkable influence on the SHG intensity. However, the specific effect on the NLO response is dependent on the type of functional group incorporated into BDC ligand, and only the inclusion of amine group that is strongly electron-donating can obviously enhance the SHG activity of MIL-125. In addition, MIL-126 and MIL-127 with longer aromatic linking unit are not suitable to act as NLO materials due to their poor phase matching abilities, but they are the promising candidates for the low dielectric constant materials. The present study can provide theoretical insights to design new second-order NLO materials based on MIL-125.
关键词： Nonlinear Optical Properties,Density Functional Theory,Hybrid Materials,Ligand Functionalization,Metal-Organic Framework,Plasmonics,Optical,Magnetic
更新于2025-09-04 15:30:14
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Carbon nanotube based metal-organic framework nanocomposites: Synthesis and their photocatalytic activity for decolorization of colored wastewater
摘要： Herein, Materials Institute Lavoisier (MIL-125(Ti))/carbon nanotube (CNT) nanoporous composites (MIL/CNT) were synthesized by hydrothermal method. Different amounts of CNT (0.01 g and 0.03 g) were used to synthesize nanocomposites (denoted as MIL/CNT(0.01) and MIL/CNT(0.03), respectively). The synthesized nanomaterials (MIL, MIL/CNT(0.01) and MIL/CNT(0.03)) were characterized by XRD, FTIR, TGA, BET, SEM, and zeta potential and used for photocatalytic dye degradation. Reactive Black 5 (RB5) was used as a model pollutant. The zeta potential of MIL and MIL/CNT (0.01) were ?27.7 mV and 19.2 mV, respectively. The data showed that that MIL/CNT(0.01) nanocomposite had higher photocatalytic dye degradation due to the synergistic effect of CNT. Dye decolorization by the nanomaterials followed the zero-order kinetics reaction. The decolorization rate was 0.0015, 0.0019, 0.0024 mg/L min for MIL, MIL/CNT(0.01) and MIL/CNT(0.03), with the correlation coefficient of 0.9639, 0.9906, and 0.9757, respectively. The synthesized catalysts were reusable over two cycles.
关键词： Metal-organic framework-carbon nanotube nanocomposite,Photocatalytic dye degradation,Reactive Black 5,Synthesis
更新于2025-09-04 15:30:14
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[Ceramic Transactions Series] Proceedings of the 12th Pacific Rim Conference on Ceramic and Glass Technology (Ceramic Transactions) || Dielectric Properties of Confined Ionic Liquids
摘要： Ionic liquids, as solvent free electrolytes, are promising materials improving the energy density of future storage devices. Two key requirements for such an application are a broad electrochemical window and a high ionic mobility of ionic liquids. A thorough measurement of the dielectric properties in a broad temperature and frequency regime allows analyzing the latter one in detail. Ionic mobility is influenced by intrinsic relaxations. These relaxations are influenced by correlation between the molecules. Confining the molecules allows to access this correlation length and to address the fundamental questions regarding supercooled liquids. We demonstrate this by confining the ionic liquid 1-butyl-3-methyl-imidazolium chloride in a metal-organic-framework, namely MFU-4. The preliminary results of an enhanced rotational motion compared to the bulk ionic liquid point towards a temperature, where the correlation length corresponds to the pore diameter of the confining host.
关键词： Ionic liquids,confinement,metal-organic-framework,BMIM-Cl,MFU-4,dielectric properties
更新于2025-09-04 15:30:14
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Z-Scheme Photocatalytic CO2 Reduction on a Heterostructure of Oxygen-Defective ZnO/Reduced Graphene Oxide/UiO-66-NH2 under Visible Light
摘要： The construction of a Z-scheme heterojunction is an effective way to isolate photogenerated electron-holes and enhance the activity of the semiconductor photocatalysts. However, the Z-scheme heterojunctions based on metal organic framework (MOF) were rarely reported. Herein, a novel oxygen-defective ZnO (O-ZnO)/reduced graphene oxide (rGO)/UiO-66-NH2 Z-scheme heterojunction has been prepared by a facile solvothermal route. The morphologies, structures and photoelectric characteristics of the acquired materials were characterized in detail. The photocatalytic activity of the O-ZnO/rGO/UiO-66-NH2 heterostructure was assessed by photocatalytic CO2 reduction. The results indicated that the O-ZnO/rGO/UiO-66-NH2 heterostructure could efficiently reduce CO2 to CH3OH and HCOOH, and its activity was significantly superior to that of O-ZnO/UiO-66-NH2 and ZnO/rGO/UiO-66-NH2. Under illumination of visible light, the yield of CH3OH and HCOOH over O-ZnO/rGO/UiO-66-NH2 heterostructure reached 34.83 and 6.41 μmol·g-1·h-1, respectively. The high photoactivity of O-ZnO/rGO/UiO-66-NH2 heterostructure should be caused by the effective spatial separation of photogenerated electrons and holes via a Z-scheme charge transfer. This research may well present an insight into the design and fabrication of novel Z-scheme photocatalytic systems for environmental remediation and energy conversion.
关键词： CO2 reduction,metal organic framework,photocatalytic,oxygen-defective,Z-scheme
更新于2025-09-04 15:30:14
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Metal-organic frameworks as SERS substrates with high tailorability
摘要： Surface enhanced Raman scattering (SERS) is a widely used analytical technique for detecting trace-level molecules based on an indispensable SERS substrate. SERS substrates with high tailorability are assumed to be attractive and desirable for SERS detection, because the substrates match the need for the selective detection of different species. Nevertheless, the rational design of such SERS substrates is rather challenging for both noble-metal and semiconductor substrates. Herein, expanding beyond conventional SERS substrates, we demonstrate that metal-organic framework (MOF) materials can serve as a type of SERS substrate with molecular selectivity, which are rarely realized for SERS detection without any special pretreatment. A salient structural characteristic of MOF-based SERS substrates benefiting the SERS selectivity is their high tailorability. By controlling the metal centers, organic ligands, and framework topologies of our MOF-based SERS substrates, we show that the electronic band structures of MOF-based SERS substrate can be purposively manipulated to match those of the target analytes, thus resulting in different detectable species. Going further, the SERS enhancement factors (EFs) of the MOF-based SERS substrates can be greatly enhanced to as high as 106 with a low detection limit of 10-8 M by pore-structure optimization and surface modification, which is comparable to the EFs of noble metals without “hot spots” and recently-reported semiconductors. This selective enhancement is interpreted as being due to the controllable combination of several resonances, such as the charge-transfer, interband and molecule resonances, together with the ground-state charge-transfer interactions. Our study opens a new venue for the development of SERS substrates with high-design flexibility, which is especially important for selective SERS detection towards specific analytes.
关键词： Surface enhanced Raman scattering (SERS),tailorability,charge-transfer,molecular selectivity,interband and molecule resonances,enhancement factors (EFs),metal-organic framework (MOF),ground-state charge-transfer interactions,SERS substrates
更新于2025-09-04 15:30:14