Study on Gas Sorption and Iodine Uptake of a Metal-Organic Framework Based on Curcumin.

Medi-MOF-1 is a highly porous Metal-Organic framework (MOF) constructed from Zn(II) and curcumin. The obtained crystal was characterized using powder X-ray diffraction (PXRD) and scanning electron microscopy (SEM). A micrometer-sized crystal with similar morphology was successfully obtained using the solvothermal method. Thanks to its high surface area, good stability, and abound pores, the as-synthesized medi-MOF-1 could be used as a functional porous material to adsorb different gases (H2, CO2, CH4, and N2) and iodine (I2). The activated sample exhibited a high I2 adsorption ability of 1.936 g g-1 at room temperature via vapor diffusion. Meanwhile, the adsorbed I2 could be released slowly in ethanol, confirming the potential application for I2 adsorption.

An Improved YOLOv5 Model: Application to Mixed Impurities Detection for Walnut Kernels.

Impurity detection is an important link in the chain of food processing. Taking walnut kernels as an example, it is difficult to accurately detect impurities mixed in walnut kernels before the packaging process. In order to accurately identify the small impurities mixed in walnut kernels, this paper established an improved impurities detection model based on the original YOLOv5 network model. Initially, a small target detection layer was added in the neck part, to improve the detection ability for small impurities, such as broken shells. Secondly, the Tansformer-Encoder (Trans-E) module is proposed to replace some convolution blocks in the original network, which can better capture the global information of the image. Then, the Convolutional Block Attention Module (CBAM) was added to improve the sensitivity of the model to channel features, which make it easy to find the prediction region in dense objects. Finally, the GhostNet module is introduced to make the model lighter and improve the model detection rate. During the test stage, sample photos were randomly chosen to test the model's efficacy using the training and test set, derived from the walnut database that was previously created. The mean average precision can measure the multi-category recognition accuracy of the model. The test results demonstrate that the mean average precision (mAP) of the improved YOLOv5 model reaches 88.9%, which is 6.7% higher than the average accuracy of the original YOLOv5 network, and is also higher than other detection networks. Moreover, the improved YOLOv5 model is significantly better than the original YOLOv5 network in identifying small impurities, and the detection rate is only reduced by 3.9%, which meets the demand of real-time detection of food impurities and provides a technical reference for the detection of small impurities in food.

Porous Organic Frameworks Constructed by the Synergetic Effect of Covalent Bonds and Hydrogen Bonds for the Selective Identification and Detection of Explosives.

Covalent organic frameworks (COFs) and hydrogen-bonded organic frameworks (HOFs) have emerged as novel platforms for material design and functional explorations. Here, we report an unconventional structural organic framework (named CHOF-1) combined with 1,3,5-tris(4-aminophenyl)benzene (TAPB) and 5-hydroxyisophthalaldehyde (HP) through the synergetic effect of covalent bonds and hydrogen bonds. CHOF-1 contains two different pores and is an eclipsed AA-stacking model with high thermal stability. It exhibits selective "turn-off" and red shift fluorescence responses toward 4-nitrophenol (4-NP) and 2,4,6-trinitrophenol (TNP) in ethanol, respectively, and the low detection limit was 8.78 µM for 4-NP and 11.1 µM for TNP. It has satisfactory recovery in the detection of 4-NP and TNP in practical water samples. The fluorescence quenching of CHOF-1 caused by 4-NP is attributed to the absorption competition quenching (ACQ) mechanism. In the structure of CHOF-1, the hydroxyl of TNP has strong acidity and can form strong hydrogen bonds with the unreacted NH2. Then, the crystalline structure of CHOF-1 decomposed and the electron structure of the photophore changed; thus, the fluorescence spectra red-shifted. This is a novel example of a covalent bond and hydrogen bonds combined organic framework (CHOF). This work not only demonstrates a synthesis strategy of the first novel structural organic framework through the synergetic effect of covalent bonds and hydrogen bonds but also provides a fluorescent sensing material for the detection of explosives 4-NP and TNP with high selectivity and sensitivity.

One-pot synthesis of tri- and di-fluoromethylated bis(indolyl)methanols via Friedel-Crafts-type acylation and alkylation.

A simple and efficient methodology for the first synthesis of tri- and di-fluoromethyl-bis(indolyl)methanols has been demonstrated through a one-pot Friedel-Crafts-type acylation-alkylation of readily available indoles and fluorinated acids. This simple protocol was successfully performed under metal-, additive-, toxic-solvent-, and protective-gas-free conditions, and delivered a wide range of tri- and di-fluoromethyl-bis(indolyl)methanols in moderate to high yields. Notably, this reaction can tolerate diverse vital and reactive functional groups. Furthermore, this one-pot Friedel-Crafts-type acylation-alkylation can be readily expanded to the gram scale with no obvious decrease in the yield, demonstrating its high application potential.

Manganese-promoted cleavage of acetylacetonate resembling the ß-diketone cleaving dioxygenase (Dke1) reactivity.

We here report a manganese-based oxidative cleavage of inactivated acetylacetonate, the mechanistic pathway of which resembles Dke1-catalyzed reactions of ß-diketone and α-keto acid. This oxidative transformation proceeds through an acetylacetonate-pyruvate-oxalate pathway, which can be terminated at the stage of pyruvate through ligand/solvent variation. XRD, time-dependent GC-MS, and isotope-labeling studies suggested that our system represents the same cleaving specificity and dioxygenase-like reactivity of Dke1.

Efficient proton conductivity of a novel 3D open-framework vanadoborate with [V6B20] architectures.

A new three-dimensional (3-D) inorganic metal-oxygen network vanadoborate Na3H10[Ni(H2O)2(VO)6(B10O22)2]·NH4·19H2O (1) constructed from lantern-type {(VO)6(B10O22)2} clusters, NaO6 polyhedra and NiO6 octahedra, was successfully synthesized by a hydrothermal method. In the structure, the {V6B20} clusters are linked together through NiO6 octahedral bridges, resulting in 1-D chains along the c-axis. The 1-D chains are further connected by NaO6 polyhedra to give rise to a 3-D open-framework structure. Furthermore, lots of NH4+ and H2O molecules are accommodated in the void of the structure, and may interact with the [V6B20] system via N-HO, O-HO hydrogen bonds, constructing a complex hydrogen-bonding network system. Strikingly, compound 1 exhibited a high proton conductivity of 3.22 × 10-3 S cm-1 at 50 °C under 100% RH with an activation energy of 1.66 eV.

An Anionic Indium-Organic Framework with Spirobifluorene-Based Ligand for Selective Adsorption of Organic Dyes.

Ionic metal-organic frameworks (MOFs) with an ionic skeleton and unique porous structures could selectively adsorb charged dyes with specific dimensions. However, the ion-exchange-based and size-exclusion-based process as a chromatography method needs to be further explored. In this study, a new microporous anionic MOF, JUC-210, was synthesized using a spirobifluorene-based ligand and trivalent metal indium. JUC-210 has a two-fold interpenetrated pts framework with a large void space, possessing suitable pore sizes and an anionic skeleton for efficient separation of certain organic dyes. Different types of dyes were used to observe the selective adsorption ability of the as-synthesized MOF. JUC-210 displayed high selective adsorption toward the cationic dye methylene blue with positive charges based on ion exchange and size exclusion. Moreover, the effect of solvent on the selective adsorption behaviors of JUC-210 was investigated. The exploration of novel MOF materials would provide potential efficient adsorbents for separation of organic dyes.

Pentanuclear clusters resembling the cubane-dangler connectivity in the native oxygen-evolving center of photosystem II.

A series of pentametallic "cubane-plus-dangler" complexes have been target synthesized. Among them, the [Fe3Ni2] aggregate strongly resembled the native oxygen-evolving center by mimicking the "cubane-plus-dangler" skeleton, the aqua binding site, and the connectivity between the pendent ion and the parent cubane. Our synthetic strategy that uses tri-substituted methanol as the "cubane-generator" and carboxylate as the pendant ligand provides a feasible approach for accessing model compounds of biological catalyst systems.

Fabrication of Crystalline Microporous Membrane from 2D MOF Nanosheets for Gas Separation.

Metal-organic frameworks (MOFs)-based membranes have shown great potentials as applications in gas separation. In this work, a uniform membrane based on 2D MOF Ni3 (HITP)2 (HITP=2,3,6,7,10,11-hexaaminotriphenylene) was fabricated on ordered macroporous AAO via the filtration method. To fabricate the membrane, we obtained the Ni3 (HITP)2 nanosheets as building blocks via a soft-physical exfoliation method successfully that were confirmed by AFM and TEM. We also studied the H2 , CO2 and N2 adsorption isotherms of Ni3 (HITP)2 powder at room temperature, which shows Ni3 (HITP)2 has high heats of adsorption for CO2 and high selectivity of CO2 over N2 . Gas permeation tests indicate that the Ni3 (HITP)2 membrane shows high permeance and selectivity of CO2 over N2 , as well as good selectivity of H2 over N2 . The ideal separation factors of CO2 /N2 and H2 /N2 from sing-gas permeances are 13.6 and 7.8 respectively, with CO2 permeance of 3.15×10-6  mol⋅m-2 ⋅s-1 ⋅Pa-1 . The membrane also showed good stability, durability and reproducibility, which are of potential interest for practical applications in the CO2 separations.

Design and Construction of a Metal-Organic Framework as an Efficient Luminescent Sensor for Detecting Antibiotics.

We first design and synthesize a dendritic aromatic 6-carboxyl linker (H6TDCPB), which is successfully assembled with Cd(II) ion to construct a porous metal-organic framework with a raw Cd6 cluster, {[Cd3(TDCPB)·2DMAc]·DMAc·4H2O}n (namely, complex 1). More interestingly, six adjacent linkers are packed together by π-π-stacking interactions to form an amazing six-molecule accumulation in the crystal structure. By virtue of high stability and luminescent properties, the as-synthesized sample not merely owns an excellent detectable ability but also possesses an outstanding selectivity for nitrofurans with remarkable recursitivity.

A Double-Walled Porous Metal-Organic Framework as a Highly Efficient Catalyst for Chemical Fixation of CO2 with Epoxides.

A double-walled MOF [Zn5(µ3-OH)2(DBTA)2(H2O)4]·solvents [1, H4DBTA = 2,2'-dihydroxy-1,1'-binaphthyl-3,3',6,6'-tetrakis(4-benzoic acid)] has been designed and constructed based on a rare Zn5 cluster. The resultant sample has enrichment of porous structure with high BET and Langmuir surface area. By virtue of multiaperture structure and plentiful catalytic sites of Brønsted (-OH) and Lewis acidic (ZnII), MOF 1 is a unique catalyst to synthesize cyclic carbonates from CO2 and epoxides with preferable repeatability.

A Molecular Coordination Template Strategy for Designing Selective Porous Aromatic Framework Materials for Uranyl Capture.

Uranium capture from seawater could solve increasing energy demand and enable a much needed relaxing from fossil fuels. Low concentration (∼3 ppb), competing cations (especially vanadium) and pH-dependent speciation prohibit highly efficient uranium uptake. Despite intensive research, selective extraction of uranyl ions over vanadyl units remains a tremendous challenge. Here, we adopted a molecular coordination template strategy to design a uranyl-specific bis-salicylaldoxime entity and decorated it into a highly porous aromatic framework (PAF-1) by programmable assembly. The superstructure (MISS-PAF-1) gives a strong affinity that removes 99.97% of uranium in 120 min. Notably, it binds to the uranyl ion at least 100 times more selectively than 14 different cations tested, including the vanadyl ion, in simulated seawater at ambient pH. Real seawater samples collected from the Bohai Sea achieve 5.79 mg g-1 of uranium capacity over 56 days without PAF degradation, exceeding a 4-fold higher amount than commercial adsorbents.

An Exceptionally Stable TbIII-Based Metal-Organic Framework for Selectively and Sensitively Detecting Antibiotics in Aqueous Solution.

An exceptionally stable metal-organic framework based on one-dimensional (1D) TbIII chains with significant green emission under excitation energy, {[Tb(TATMA)(H2O)·2H2O} n (namely, 1), has been fabricated successfully under hydrothermal conditions. By virtue of the spectral overlap between the absorbance spectra of nitrofurans (NFAs) and the excitation spectrum of MOF 1, the resultant sample exhibits outstandingly sensitive and selective luminescence detectability for NFT ( Ksv = 3.35 × 104 M-1) and NFZ ( Ksv = 3.00 × 104 M-1) by quenching phenomenon. More importantly, it can detect NFAs in water from bovine serum samples. The portable MOF film can be easily prepared and used with excellent stability and recursitivity.

A Highly Crystalline Fluorene-Based Porous Organic Framework with High Photoluminescence Quantum Yield.

Using 4-connected pyrene-based building blocks with D2h symmetry and 2-connected fluorene-based linker with C2v symmetry, a 2D porous organic framework is obtained via imine condensation, PAF-130. PAF-130 has high crystallinity, permanent, and a high photoluminescence quantum yield, which is as high as 29.5% when dispersed in acetonitrile.

Facile Synthesis of Ultrastable Porous Aromatic Frameworks by Suzuki-Miyaura Coupling Reaction for Adsorption Removal of Organic Dyes.

Porous aromatic frameworks (PAFs) with robust structure, high stability, and high surface area have attracted intense interest from scientists in diverse fields. However, there are still very few reports on the adsorption of organic dyes by PAFs. In this work, four new PAFs have been facilely synthesized by the polymerization of a tetrahedral-shaped (four-node) monomer with a series of three-node monomers through Suzuki-Miyaura coupling reactions. All the obtained materials possess hierarchical porous structures and show high thermal and chemical stability. The Brunauer-Emmett-Teller (BET) surface areas of these PAFs were determined to be 857 m2 g-1 for PAF-111, 526 m2 g-1 for PAF-112A, 725 m2 g-1 for PAF-112B, and 598 m2 g-1 for PAF-113. Rhodamine B was selected as a model organic dye to test the adsorption capacities of the obtained PAF materials. PAF-111 showed a maximum adsorption capacity of 1666 mg g-1 (167 wt %) for Rhodamine B, which is among the highest values reported to date for porous organic materials. It is noteworthy that PAF-111 could be reused in at least ten cycles under the adsorption conditions without any loss of adsorption capacity. Our study has revealed the great potential and advantages of PAFs as ultrastable adsorption materials for the removal of organic dyes.

Construction of Porous Aromatic Frameworks with Exceptional Porosity via Building Unit Engineering.

The construction of excellent porous organic frameworks (POFs) with high surface areas and stability is always a tremendous challenge in synthetic chemistry. The geometric configuration and reactive group of building unit are crucial factors to influence the structure and porosity of the resulting product. Herein, the design, synthesis, and characterization of two porous aromatic framework (PAF) materials, named PAF-100 and PAF-101, are reported via a strategy of building unit engineering. PAF-100 and PAF-101 present high Brunauer-Emmett-Teller surface areas exceeding 5000 m2 g-1 and uniform pore size distributions. Furthermore, PAF-100 and PAF-101 show high methane uptake with value of 742 and 622 cm3 g-1 , respectively, at 298 K and 70 bar. The successful synthesis of PAFs with exceptional porosity from engineered building unit is powerful for constructing highly porous POFs.

A Versatile Microporous Zinc(II) Metal-Organic Framework for Selective Gas Adsorption, Cooperative Catalysis, and Luminescent Sensing.

A versatile microporous zinc(II) MOF (1) with plentiful Lewis basic sites and open metal sites synchronously has been synthesized successfully. The resultant microporous material displays excellent selectivity adsorption for small gases. The IAST selectivity values for CO2/CH4, C2H6/CH4, CO2/N2, and C3H8/CH4 are 7, 21, 38, and 125 at 101 kPa and 298 K, respectively. 1 exhibits remarkably heterogeneous catalytic performance for acid-base one-pot reactions. Furthermore, 1 exhibits recyclable selective detectability for TNP. The results illustrate that 1 is a versatile material for selective gas adsorption, cooperative catalysis, and luminescent sensing.

Single-Electron Oxidation/Alterable C3- and C10-Arylation of 9-MeO-phenanthrene.

A reactivity pattern for C3-arylation of 9-MeO-phenanthrene has been established for the first time by using 2-naphthyl amines as coupling partners. A series of phenanthrene- and naphthalene-based multifunctionalized polycyclic aromatic hydrocarbons have been obtained in good to excellent yields. Alternative C10-arylation of 9-MeO-phenanthrene has also been accomplished, using 2-naphthalenol derivatives as coupling partners. Trifluoroacetic acid is found crucial for the regioselectivity. Density functional theory calculations and electrochemical analyses have been performed to rationalize the reaction mechanism.

Porous aromatic framework with mesopores as a platform for a super-efficient heterogeneous Pd-based organometallic catalysis.

A strategy using a mesoporous amine-tagged porous aromatic framework (PAF70-NH2 ) to immobilize a palladium (Pd)-based molecular catalyst has been developed. The resulting immobilized catalyst PAF70-Pd, in which the framework is entirely constructed by phenyl rings linked with stable carbon-carbon bonds, has high structural rigidity and stability. Compared with the known porous organic material immobilized Pd-based catalysts, PAF70-Pd has the highest Pd content so far. Moreover, PAF70-Pd has extremely high catalytic activity with good size selectivity and very easy recyclability in catalyzing the Suzuki-Miyaura coupling reaction. In the current system, the catalyst loading could be as low as 0.001 mol% and the TOF value could go up to 28 800 h-1 which is far higher than those of the known porous organic material immobilized Pd-based catalysts. In order to elucidate the particularly high catalytic efficiency of PAF70-Pd, we prepared PAF1-Pd from PAF1-NH2 for comparison. PAF1-Pd has a higher Pd content than PAF70-Pd. However, due to the absence of large enough mesopores in PAF1-NH2 , PAF1-Pd has almost no catalytic activity under the same conditions, which definitely demonstrated that the intrinsic mesoporosity of PAF70-NH2 plays a crucial role in the superb catalytic efficiency of PAF70-Pd. This strategy to immobilize Pd-based molecular catalysts has very good expansibility to be applied in the immobilization of different organometallic catalysts into the pores of PAFs, which also has very high potential in the chemical and pharmaceutical industry.

A Stable Metal-Organic Framework Featuring a Local Buffer Environment for Carbon Dioxide Fixation.

A majority of metal-organic frameworks (MOFs) fail to preserve their physical and chemical properties after exposure to acidic, neutral, or alkaline aqueous solutions, therefore limiting their practical applications in many areas. The strategy demonstrated herein is the design and synthesis of an organic ligand that behaves as a buffer to drastically boost the aqueous stability of a porous MOF (JUC-1000), which maintains its structural integrity at low and high pH values. The local buffer environment resulting from the weak acid-base pairs of the custom-designed organic ligand also greatly facilitates the performance of JUC-1000 in the chemical fixation of carbon dioxide under ambient conditions, outperforming a series of benchmark catalysts.