Monthly Archives: October 2023

Dispersing LiCl in Zwitterionic COF for Highly Efficient Ammonia Storage and Separation

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Dispersing LiCl in Zwitterionic COF for Highly Efficient Ammonia Storage and Separation

A zwitterionic covalent organic frameworks (COF) is proposed as a porous hosts to disperse LiCl for highly efficient NH3 storage and separation. The anionic and cationic groups in zwitterionic COF act as two separated positive and negative charged sites to facilitate the dispersion of lithium chloride, which makes LiCl doped zwitterionic COF exhibit excellent NH3 capture performance.


Abstract

Efficient and inherently safe NH3 storage and separation are of significant importance for the chemical industry. Herein, we proposed zwitterionic COF as a porous host to disperse LiCl for highly efficient NH3 storage and separation with record adsorption capacity. The equivalently cationic and anionic groups in the channels of zwitterionic COF could act as two separated sites to facilitate the dispersion of LiCl, hence the optimal composite exhibits a high capture capacity of 44.98 mmol/g at 25 °C and 1 bar, far exceeding other existing porous materials. Notably, the adsorption capacity is completely reversible and the efficient separation of NH3 from NH3/CO2/N2 mixture is achieved through breakthrough experiments. DFT calculation combined with XPS and 7Li NMR experimental results give insight into the interaction between zwitterionic COF and LiCl. This work extends possibilities for the development of efficient adsorbents for NH3 storage and separation.

In‐Situ Growth of Cu2S‐MoS2 Bimetallic Electrocatalyst on Carbon Cloth for Hydrogen Evolution Reaction

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Hydrogen evolution reaction (HER) is one of prospective methods to produce hydrogen energy, and the key technology of which lies in the preparation of electrocatalysts. Preparations of catalysts with high efficiency, low price and good stability are expected. In this work, a new polyoxometalate-based copper-organic framework, [{CuII(C10N6H7)4(H2O)2}H6(PMo12O40)2]·12H2O (1) [C10N6H7: 3-(1H-pyrazol-4-yl)-5-(pyridin-4-yl)-1,2,4triazole], was synthesized as an electrocatalyst precursor, and confirmed by infrared spectroscopy (IR), single-crystal X-ray diffraction (SXRD) and X-ray powder diffraction (PXRD). A newelectrocatalyst (Cu2S-MoS2@CC-1) was synthesized from 1, thiourea (TU) and carbon cloth (CC) by a one-pot hydrothermal method. Tue to the synergistic effects between Cu2S and MoS2, the Cu2S-MoS2@CC-1 catalyst exhibits high electrocatalytic HER activity and goodstability in 0.5 M H2SO4. Namely, Cu2S-MoS2@CC-1 shows low overpotential of 150 mV@10 mA·cm-2 vs reversible hydrogen electrode (RHE) and small Tafel slope of 61 mV dec-1, and remains good stability at least 94 h and over 1000 catalytic cycles. This method provides a promising strategy for development of non-noble metal catalysts.

High Mannose Oligosaccharide Hemimimetics that Recapitulate the Conformation and Binding Mode to Concanavalin A, DC‐SIGN and Langerin

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The "carbohydrate chemical mimicry" exhibited by sp2-iminosugars has been utilized to develop practical syntheses for analogs of the branched high-mannose-type oligosaccharides (HMOs) Man3 and Man5. In these compounds, the terminal nonreducing Man residues have been substituted with 5,6-oxomethylydenemannonojirimycin (OMJ) motifs. The resulting oligomannoside hemimimetic accurately reproduce the structure, configuration, and conformational behavior of the original mannoligosaccharides, as confirmed by NMR and computational techniques. Binding studies with mannose binding lectins, including concanavalin A, DC-SIGN, and langerin, by enzyme-linked lectin assay and surface plasmon resonance revealed significant variations in their ability to accommodate the OMJ unit in the mannose binding site. Intriguingly, OMJMan segments demonstrated "in line" heteromultivalent effects during binding to the three lectins. Similar to the mannobiose (Man2) branches in HMOs, the binding modes involving the external or internal monosaccharide unit at the carbohydrate binding domain exist in equilibrium, facilitating sliding and recapture processes. This equilibrium, which influences the multivalent binding of HMOs, can be finely modulated upon incorporation of the OMJ sp2-iminosugar caps. As a proof of concept, the affinity and selectivity towards DC-SIGN and langerin were adjustable by presenting the OMJMan epitope in platforms with diverse architectures and valencies.

Preparation of Mono and Bis‐Hydrazino‐Substituted N‐Heterocyclic Carbene Boranes

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We report the formation of NHC complexes of mono- and bis-hydrazino boranes with N–N–B and N–N–B–N–N chains via the reaction of NHC-boranes with electrophilic azo reagents. The influence of steric hindrance on the carbene and on the azo reagent has been shown to be crucial for the reactivity. The hydroboration of dissymmetric azo reagents is regioselective only when the latter is sufficiently electronically twisted. Bis-hydrazino borane complexes with two different hydrazine arms could be obtained via sequential addition.

Biological properties of cyclitols and their derivatives

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Cyclitols are polyhydroxy cycloalkanes, each containing at least three hydroxyls attached to a different ring carbon atom, and its general formula is CnH2n-x(OH)x or CnH2nOx. The most important cyclitol derivatives are inositols, quersitols, conduritols and pinitols, which form a group of naturally occurring polyhydric alcohols and are widely found in plants. In addition, synthetic production of cyclitols has gained importance in recent years. Cylitols are molecules synthesized in plants as a precaution against salt or water stress. They have important functions in cell functioning as they exhibit important properties such as membrane biogenesis, ion channel physiology, signal transduction, osmoregulation, phosphate storage, cell wall formation and antioxidant activity. The biological activities of these very important molecules, obtained both synthetically and from the extraction of plants, are described in this review.

Surface Plasmon Resonance (SPR)‐Triggered Polarization of BaTiO3 Surface on Ag Nanocubes Improves Photocatalysis

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The SPR-generated electric field (E-field) intensities around a Ag nanocube (NC) before and after covered by BaTiO3 (BTO) layer (BTO@Ag NC) were calculated. It was observed that the theoretical E-field intensities were reduced on BTO@Ag NC, thus suggesting inferior catalytic activities under visible light illumination. However, BTO@Ag NCs experimentally displayed better photocatalytic performance than that of Ag NCs under illumination at 633 nm, both in ambient argon (Ar) and in ambient air, where PATP molecules were used to probe the conversion. The mechanism can be attributed to the surface polarization of BTO layer trigged by SPR effect of Ag core. The oscillation of free electrons in Ag core aroused appearance of surface polarization charge on ferroelectric (FE) BTO surface, which resulted in the enhanced catalytic properties of BTO@Ag NCs. Therefore, our finding may provide a novel method to enhance visible-light responsive photocatalytic activity of wide bandgap FE materials by depositing them on plasmonic metal nanostructures.

Porous Core‐membrane Microstructured Nanomaterial Composed of Deep Eutectic Solvents and MOF‐808 for CO2 Capture

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Porous Core-membrane Microstructured Nanomaterial Composed of Deep Eutectic Solvents and MOF-808 for CO2 Capture

A kind of ionic liquid, namely deep eutectic solvents, are introduced to load on the surface of porous MOF-808 core as membranes to construct porous core-membrane microstructured nanomaterials for CO2 capture at room temperature with the sorption mechanism coupling of diffusion, physisorption, and chemisorption. It shows excellent development potential for future application in CO2 capture.


Abstract

A series of porous core-membrane microstructured nanomaterials, constructed of a deep eutectic solvent (DES) membrane and porous MOF-808 core via liquid surface tensions and electrostatic interactions, are introduced for carbon dioxide capture with the sorption mechanism coupling diffusion, physisorption, and chemisorption. MOF-808 as the porous core considerably improves the diffusion interactions for DES membranes, hence significantly enhancing the sorption performance of DESs. Although the DES consisted by monoethanolamine and tetrapropylammonium chloride (MEA-TPAC-7) has the highest sorption capacity among all DESs, it is only 4.39 mmol g−1 at 2.4 bar and further attenuates by fastidious diffusion interactions when increasing viscosity or dose. The sorption capacities of DES@MOF-120 are 5.18 mmol g−1 at 3.0 bar and 4.78 mmol g−1 at 2.4 bar without apparent sorption hysteresis in pressure swing sorption, which are substantially improved contrasted to MEA-TPAC-7. The sorption isotherms are reconstructed via Sips models considering surface heterogeneity with regression correlation coefficients over 0.9454 to forecast maximum sorption capacity over 6.33 mmol g−1.

Solid‐State Absorption, Luminescence, and Singlet Fission of Furanyl‐Substituted Diketopyrrolopyrroles with Different π‐Stacking Arrangements

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Solid-State Absorption, Luminescence, and Singlet Fission of Furanyl-Substituted Diketopyrrolopyrroles with Different π-Stacking Arrangements

Furanyl-substituted diketopyrrolopyrroles (DPP) with different branching of the alkyl side chains were studied. Both formed two distinct types of π-stacking leading to H-aggregates with considerably different energetics in terms of mixed lowest Frenkel and charge transfer (CT) states. The combined effect of the molecular structure and solid-state arrangement lead to fast and efficient CT mediated singlet fission, with one of the highest efficiencies (160 %) ever reported within the DPP family.


Abstract

Small modifications of the diketopyrrolopyrrole (DPP) molecular structure induced remarkable changes in its spectral and photophysical behavior. Using furan (F) heterosubstitution instead of thiophene (T) substituent resulted in a small blue shift and decreased Huang-Rhys factor of the absorption spectra in solution, irrespectively to N,N'-alkyls. Branching of alkyl side chains by formal 2-ethylation of n-hexyl substituent (C6 to EH) switched the slipped-stack arrangement, irrespectively on the heteroatoms. Consequent changes in steady-state absorption spectra of thin films were interpreted using time dependent density functional theory calculations, carried out on model dimers. Solid-state luminescence is weak and partially dependent on an excitation wavelength. Singlet fission was observed by femtosecond transient absorption spectroscopy, with considerably different yields for variously π-stacked FDPP-EH (30 %) and FDPP-C6 (160 %). The shape of triplet-triplet absorption spectra was also influenced by various π-stacking. The results are discussed in terms of different mixing of both Frenkel and charge transfer states in model dimers and different excitonic and electronic coupling in both types of π-stacks, visualized by natural transition orbitals.

Environmental Feasibility Analysis for the Acrylonitrile Production from Glycerol

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Environmental Feasibility Analysis for the Acrylonitrile Production from Glycerol

The application of the life cycle assessment technique for the acrylonitrile production from glycerol is proposed with propylene or glycerol as the main feedstock to compare the results, aiming at evaluating the environmental impacts generated in the process. The glycerol-based process from two sources (soybean, waste cooking oil) demonstrated promise in reducing fossil fuels and water consumption.


Abstract

Acrylonitrile is a monomer traded as a commodity on the global market with applications in several industrial sectors, produced from the ammoxidation of propylene. New technological alternatives are being studied, reducing the use of petroleum derivatives through renewable raw materials. This article proposes the application of the life cycle assessment technique for acrylonitrile production from glycerol, with the objective of evaluating the environmental impacts generated in the process. The results demonstrated that the use of glycerol from the state of Mato Grosso can reduce consumption of fossil fuel and water by 45 % and 31 %, respectively. The results about greenhouse gas (GHG) emissions were little significant when replacing the raw material.

Biochar‐MgO from Soursop Seeds in Production of Biofuel Additive Intermediates.

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The conversion of residual biomass from fruit seeds into biochar can be achieved using MgCl2 as an activating agent and calcining at 700 °C. The resulting MgO-biochars were employed in the aldol condensation reaction between furfural and acetone. This reaction is essential as the first step in the obtention of biofuels derived from biomass. The biochars were characterized through various physicochemical techniques, revealing that the presence of MgO nanoparticles deposited on the carbon surface modifies the structural and acidic-basic properties of the carbonaceous materials with a graphitic structure. The biochar with a surface content of MgO of 0.34% w/w enables the achievement of 100% of selectivity towards 4-(2-furanyl)-3-buten-2-one (I) with quantitative conversions under optimized conditions. This property highlights the potential of using this type of biochar, commonly used for CO2 capture, as a versatile acidic-basic catalyst, thereby introducing a novel approach to sustainable chemistry.