Amino‐Induced 2D Cu‐Based Metal–Organic Framework as an Efficient Heterogeneous Catalyst for Aerobic Oxidation of Olefins

Low background dual-ligand Cu-MOF nanoprobe for plant tissue imaging and fast screening as well as sensitive detection of glyphosate in environmental samples

The monitoring of glyphosate residue in environmental samples is critically important due to its high environmental risk. Here, we reported a low background dual-ligand and fast response copper-based metal organic framework (Cu-MOF) nanoprobe for imaging glyphosate in plant tissue, rapid screening of glyphosate-contaminated samples, and sensitive detection of glyphosate in environmental samples. The Cu-MOF nanoprobe was prepared with 2-Aminoisophthalic Acid (AIA) and trimesic acid (H3BTC) as ligands, and Cu2+ as a metal node. Thanking to both ligand-to-metal charge transfer (LMCT) and photoinduced electron transfer (PET) effects, the fluorescence of ligand AIA could be fully quenched in Cu-AIA/BTC probe. Upon the addition of glyphosate, it competed with the ligands in Cu-AIA/BTC probe, causing the collapse of MOF structure and the release of ligand AIA with obvious fluorescence recovery. This nanoprobe exhibited a desirable linear response for glyphosate in the concentration range of 0.1-80 μM, with a low detection limit of 33 nM, much lower than the maximum contaminant level (4.1 μM) set by the U.S. Environmental Protection Agency (EPA). Furthermore, it was also successfully applied for plant tissue imaging, fast screening of glyphosate-contaminated samples and monitoring of the degradation of glyphosate on tea leaves and in soil, indicating the broad application prospect of the nanoprobe.

Synthesis of UiO-66-Sal-Cu(OH)2 by a Simple and Novel Method: MOF-Based Metal Thin Film as a Heterogeneous Catalyst for Olefin Oxidation

Metal-organic frameworks (MOFs), particularly UiO-66-NH₂, are employed as a catalyst in many industrial catalyst applications. As converting catalysts into thin film significantly increases their catalytic properties for the epoxidation of olefins, we report a general approach to synthesizing MOF thin films (UiO-66-Sal-Cu(OH)₂). Using the postsynthesis method (PSM), UiO-66-NH₂ was functionalized with salicylaldehyde and entrapped on copper hydroxide nanoparticle surfaces using a modern strategy (MOF thin film). We used field-emission scanning electron microscopy (FE-SEM), EDX (energy-dispersive X-ray analysis), XRD (X-ray diffraction), FT-IR (Fourier transform infrared), BET (Brunauer-Emmett-Teller), TGA (thermogravimetric analysis), XPS (X-ray photoelectron spectroscopy), and ICP-MS (inductively coupled plasma mass spectrometry) to determine the structure and morphology of the synthesized UiO-66-Sal-Cu(OH)₂. The oxidation of cyclooctene by the UiO-66-Sal-Cu(OH)₂ thin film was studied. Due to its advantages, such as being environmentally friendly (base metal-loaded catalyst, room temperature, solvent-free reaction), reusability, and high yield, this compound can be an appropriate catalyst for the oxidation of olefins.

Emerging Two-Dimensional-Based Nanostructured Catalysts: Applications in Sustainable Organic Transformations

The extension of green and sustainable materials in the preparation of heterogeneous catalysts for organic transformations has increased over the past few decades. Because of their unique and intriguing physical and chemical properties, two-dimensional (2D) nanostructured materials have attracted widespread attention and have been used in a variety of applications, such as catalysis, electronics, and energy storage. A promising pathway to enhance the performance of 2D nanomaterials is their coupling with other functional materials to form heterogeneous or hybrid structures. Herein, we discuss the use of 2D-based nanostructured catalysts for enhancing organic transformations and highlight selected examples to demonstrate the synthesis, advantages, challenges, efficiency, and reusability of the introduced heterogeneous catalysts for cross-coupling and reduction reactions.

Ultrathin 2D Eu3+@Zn-MOF Nanosheets: A Functional Nanoplatform for Highly Selective, Sensitive, and Visualized Detection of Organochlorine Pesticides in a Water Environment

Facile and rapid detection of residual organic pesticides on the fruits and vegetables has recently drawn increased attention in the food safety field. Herein, a surfactant-assisted solvothermal route with subsequent post-modification was designed for the preparation of Eu³⁺-functionated Zn-BDC ultrathin nanosheets (labeled as Eu³⁺@Zn-MOF-NS, BDC: 1,4-benzenedicarboxylate) with the thickness of 5 nm. The as-obtained Eu³⁺@Zn-MOF-NS could be homogeneously dispersed in aqueous systems to form a highly-stable collosol. Under the UV excitation of 325 nm, the as-obtained Eu³⁺@Zn-MOF-NS displayed red photoluminescence emission of Eu³⁺ ions, which could be notably quenched by an organochlorine pesticide, 2,6-dichloro-4-nitroaniline (DCNA), without interferences from ions, organic small molecules, and other pesticides. The detection limit and K_sv were 0.17 μM (35 ppb) and 3.2 × 10⁵ M^-1 in the water system, respectively. Moreover, the present 2D Eu³⁺@Zn-MOF sensor was also employed for the detection of DCNA in Chaohu Lake water and tap water and in apple, cabbage, and pakchoi samples with the relative standard deviation (RSD) ranging from 4.74 to 9.77%. Further investigations revealed that the competitive absorption between DCNA and the as-obtained Eu³⁺@Zn-MOF-NS resulted in the fluorescence quenching of the probe.

Azo-Functionalized Zirconium-Based Metal-Organic Polyhedron as an Efficient Catalyst for CO2 Fixation with Epoxides

Chemical fixation of CO₂ as C1 source at ambient temperature and low pressure is an energy-saving way to make use of the green-house gas, but it still remains a challenge since efficient catalyst with high catalytic active sites is required. Here, a novel monoclinic azo-functionalized Zr-based metal-organic polyhedron (Zr-AZDA) has been prepared and applied in CO₂ fixation with epoxides. The inherent azo groups not only endow Zr-AZDA with good solubilization, but also act as basic sites to enrich CO₂ showing efficient synergistic catalysis as confirmed by TPD-CO₂ analysis. XPS results demonstrate that the Zr active sites in Zr-AZDA possess suitable Lewis acidity, which satisfies both substrates activation and products desorption. DFT calculation indicates the energy barrier of the rate-determining step in CO₂ cycloaddition could be reduced remarkably (by ca. 60.9 %) in the presence of Zr-AZDA, which may rationalize the mild and efficient reaction condition employed (80 °C and 1 atm of CO₂ ). The work provides an effective multi-functional cooperative method for improvement of CO₂ cycloaddition.

A novel two-dimensional metal-organic framework as a recyclable heterogeneous catalyst for the dehydrogenative oxidation of alcohol and the N-arylation of azole compounds

A novel metal–organic framework (MOF) with two-dimensional (2D) crystal structure was developed using Cu(NO₃)₂·3H₂O and 2,2′,5,5′-tetramethoxy-[1,1′-biphenyl]-4,4′-dicarboxylic acid. Further, its structure was characterized using infrared spectroscopy, thermogravimetry, X-ray diffraction, and X-ray crystallography. The activated Cu-MOF was used to catalyze the dehydrogenative oxidation of alcohol and N-arylation of azole compounds. Furthermore, it could be easily recovered and reused.

A novel metal–organic framework (MOF) with two-dimensional (2D) crystal structure was developed using Cu(NO₃)₂·3H₂O and 2,2′,5,5′-tetramethoxy-[1,1′-biphenyl]-4,4′-dicarboxylic acid.

Design of a heterometallic Zn/Ca-MOF decorated with alkoxy groups on the pore surface exhibiting high fluorescence sensing performance for Fe3+ and Cr2O72−

Reported herein is a heterometallic Zn/Ca-MOF decorated with alkoxy groups on the pore surface exhibiting high fluorescence sensing performance for Fe³⁺ and Cr₂O₇²⁻.

Bimetallic Au–Pd alloy nanoparticles supported on MIL-101(Cr) as highly efficient catalysts for selective hydrogenation of 1,3-butadiene

Gold–palladium (Au–Pd) bimetallic nanoparticle (NP) catalysts supported on MIL-101(Cr) with Au : Pd mole ratios ranging from 1 : 3 to 3 : 1 were prepared through coimpregnation and H₂ reduction. Au–Pd NPs were homogeneously distributed on the MIL-101(Cr) with mean particle sizes of 5.6 nm. EDS and XPS analyses showed that bimetallic Au–Pd alloys were formed in the Au(2)Pd(1)/MIL-101(Cr). The catalytic performance of the catalysts was explored in the selective 1,3-butadiene hydrogenation at 30–80 °C on a continuous fixed bed flow quartz reactor. The bimetallic Au–Pd alloy particles stabilized by MIL-101(Cr) presented improved catalytic performance. The as-synthesized bimetallic Au(2)Pd(1)/MIL-101(Cr) with 2 : 1 Au : Pd mole ratio showed the best balance between the activity and butene selectivity in the selective 1,3-butadiene hydrogenation. The Au–Pd bimetallic-supported catalysts can be reused in at least three runs. The work affords a reference on the utilization of a MOF and alloy nanoparticles to develop high-efficiency catalysts.

Bimetallic Au–Pd alloy particles stabilized by MIL-101(Cr) showed high activity and butene selectivity for 1,3-butadiene hydrogenation reaction.

Metal–organic frameworks for the energy-related conversion of CO2 into cyclic carbonates

MOFs are promising heterogeneous catalysts for chemical fixation of CO₂ and epoxides into cyclic carbonates.