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.

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.

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.

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.

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.

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.

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.

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.

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.

Facile synthesis of an ultra-stable metal-organic framework with excellent acid and base resistance.

A novel ultra-stable metal-organic framework, MCIF-1, [Cu2(DCI)2](MeCN), based on dicyanoimidazole and Cu(i), has been synthesized at room temperature successfully. MCIF-1 shows excellent water stability and can retain crystallinity after soaking in water for about one week. In addition, MCIF-1 also shows exceptional resistance under both acidic and basic conditions within a large pH range from 0 to 13.5. What is more, after modifying the synthesis procedure slightly, we can produce this material in a large scale during a very short time. Mild synthesis conditions, excellent stability and ease of large scale production give MCIF-1 great potential for practical use.

An Amino-Coordinated Metal-Organic Framework for Selective Gas Adsorption.

A novel 3D porous metal organic framework, JUC-141, constructed by 5-aminoisophthalic acid and Cu(NO3)2, has been synthesized successfully. The carboxyl groups in the ligand coordinate to Cu2+ to form the classic Cu2(COO)4 paddle wheel SBU, and the assembly of the SBUs with the isophthalic acid moieties leads to a kagome lattice. Interestingly, the amino groups in the ligand also take part in the coordination and link to the dipole of the paddle wheel as pillars, thus forming a 3D porous framework with eea topology. The sizes of the channels are 5.2 Å in the direction of [111] and 10.9 Å in the direction of [001]. Gas sorption tests show that the CO2 adsorption capacities of JUC-141 are 79.94 and 51.39 cm3 g-1 at 273 and 298 K under 1 atm pressure, respectively. However, the N2 adsorption capacities of JUC-141 are 13.90 and 6.76 cm3 g-1 at 273 and 298 K under 1 atm pressure, respectively. IAST calculations indicate that the selectivity values of CO2/N2 are 21.62 at 273 K and 27.60 at 298 K under 101 kPa, respectively. Good selective adsorption of CO2 over N2 makes JUC-141 possible for CO2 storage and separation.

Reticular Synthesis of a Series of HKUST-like MOFs with Carbon Dioxide Capture and Separation.

We reported a series of HKUST-like MOFs based on multiple copper-containing secondary building units (SBUs). Compound 1 is constructed by two SBUs: Cu2(CO2)4 paddle-wheel SBUs and Cu2I2 dimer SBUs. Compound 2 has Cu2(CO2)4 paddle-wheel SBUs and Cu4I4 SBUs. Furthermore, compound 3 possesses Cu2(CO2)4 paddle-wheel SBUs, Cu2I2 dimer SBUs, and Cu(CO2)4 SBUs. These compounds are promising materials for CO2 capture and separation, because they all display commendable adsorption of CO2 and high selectivity for CO2 over CH4 and N2. It is worthy to note that compound 1 exhibits the highest Brunauer-Emmett-Teller surface area (ca. 901 m(2) g(-1)) among the MOF materials based on CuxIy SBUs. In addition, compound 3 is the first case that three copper SBUs coexist in MOFs.

Deprotonation-triggered Stokes shift fluorescence of an unexpected basic-stable metal-organic framework.

A new three-dimensional porous metal-organic framework, JUC-119, constructed by a pyrene-based dendritic organic linker, H8TIAPy (H8TIAPy = 1,3,6,8-tetrakis(3,5-isophthalic acid)pyrene), and Eu(III) has been synthesized successfully. JUC-119 shows unexpected stability under a wide range of basic conditions from 0 to 0.01 M NaOH. Furthermore, with two carboxyl groups uncoordinated in each ligand, the crystals of JUC-119 show deprotonation-triggered Stokes shift fluorescence under basic conditions. As the concentration of base increases from 0 to 0.01 M NaOH, the luminescence emission of JUC-119 becomes gradually red shifted from 455 to 485 nm. In addition, the Stokes shift shows a good linear relationship to -log[OH(-)], which makes JUC-119 promising for base sensing.

The adsorption and simulated separation of light hydrocarbons in isoreticular metal-organic frameworks based on dendritic ligands with different aliphatic side chains.

Three isoreticular metal-organic frameworks, JUC-100, JUC-103 and JUC-106, were synthesized by connecting six-node dendritic ligands to a [Zn4O(CO2)6] cluster. JUC-103 and JUC-106 have additional methyl and ethyl groups, respectively, in the pores with respect to JUC-100. The uptake measurements of the three MOFs for CH4, C2H4, C2H6 and C3H8 were carried out. At 298 K, 1 atm, JUC-103 has relatively high CH4 uptake, but JUC-100 is the best at 273 K, 1 atm. JUC-100 and JUC-103 have similar C2H4 absorption ability. In addition, JUC-100 has the best absorption capacity for C2H6 and C3H8. These results suggest that high surface area and appropriate pore size are important factors for gas uptake. Furthermore, ideal adsorbed solution theory (IAST) analyses show that all three MOFs have good C3H8/CH4 and C2H6/CH4 selectivities for an equimolar quaternary CH4/C2H4/C2H6/C3H8 gas mixture maintained at isothermal conditions at 298 K, and JUC-106 has the best C2H6/CH4 selectivity. The breakthrough simulations indicate that all three MOFs have good capability for separating C2 hydrocarbons from C3 hydrocarbons. The pulse chromatographic simulations also indicate that all three MOFs are able to separate CH4/C2 H4/C2H6/C3H8 mixture into three different fractions of C1, C2 and C3 hydrocarbons.

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.

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.

pH-Triggered controlled drug release from mesoporous silica nanoparticles via intracelluar dissolution of ZnO nanolids.

Acid-decomposable, luminescent ZnO quantum dots (QDs) have been employed to seal the nanopores of mesoporous silica nanoparticles (MSNs) in order to inhibit premature drug (doxorubicin) release. After internalization into HeLa cells, the ZnO QD lids are rapidly dissolved in the acidic intracellular compartments, and as a result, the loaded drug is released into the cytosol from the MSNs. The ZnO QDs behave as a dual-purpose entity that not only acts as a lid but also has a synergistic antitumor effect on cancer cells. We anticipate that these nanoparticles may prove to be a significant step toward the development of a pH-sensitive drug delivery system that minimizes drug toxicity.

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.

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.