Porphyrin-Based Metal-Organic Framework Materials: Design, Construction, and Application in the Field of Photocatalysis.

Metal-organic frameworks (MOFs) are a novel category of porous crystalline materials with an exceptionally high surface area and adjustable pore structure. They possess a designable composition and can be easily functionalized with different units. Porphyrins with conjugated tetrapyrrole macrocyclic structures can absorb light from ultraviolet to visible light regions, and their structures and properties can be facilely regulated by altering their peripheral groups or central metal ions. Porphyrin-based MOFs constructed from porphyrin ligands and metal nodes combine the unique features of porphyrins and MOFs as well as overcoming their respective limitations. This paper reviewed the design and construction, light absorption and charge transfer pathways, and strategy for improving the photocatalytic performance of porphyrin-based MOFs, and highlighted the recent progress in the field of CO2 reduction, hydrogen evolution, organic synthesis, organic pollutant removal, and nitrogen fixation. The intrinsic relationships between the structure and the property of porphyrin-based MOFs received special attention, especially the relationships between the arrangements of porphyrin ligands and metal nods and the charge transfer mechanism. We attempted to provide more valuable information for the design and construction of advanced photocatalysts in the future. Finally, the challenges and future perspectives of the porphyrin-based MOFs are also discussed.

Development of environmentally friendly glyoxal-based adhesives with outstanding water repellency utilizing wheat gluten protein.

To reduce the release of volatile organic compounds (VOCs) from formaldehyde-based adhesives at the source, the use of low-toxicity and biodegradable glyoxal instead of formaldehyde for the preparation of novel urea-glyoxal resins is a simple and promising strategy. The limited water resistance and adhesive strength of the new urea-glyoxal resins (UG) restrict their extensive application. This study prepared a high-performance, water-resistant WP-UG wood adhesive by combining UG prepolymer with wheat gluten protein (WP). FTIR, XRD, and XPS confirmed the existence of a chemical reaction between the two components, and thermal analysis showed that WP-UG plywood had better thermal stability. Evaluation of the gluing properties revealed that the dry and wet strengths of WP-UG adhesive bonded plywood reached 1.39 and 0.87 MPa, respectively, which were significantly higher than those of UG resin by 35 % and 314 %. The bond strength increased from 0 to 0.89 MPa after immersion in water at 63 °C for 3 h. The results indicated that the introduction of WP promoted the formation of a more complex and tightly packed crosslinking network and developed a glyoxal-based adhesive with high bond strength and water resistance. This study provides a new green pathway for novel urea-formaldehyde binders to replace harmful formaldehyde-based binders, which helps to increase their potential application value in the wood industry.

Structuring restricted amorphous molecular chains in the reinforced cellulose film by uniaxial stretching.

The construction of the preferred orientation structure by stretching is an efficient strategy to fabricate high-performance cellulose film and it is still an open issue whether crystalline structure or amorphous molecular chain is the key factor in determining the enhanced mechanical performance. Herein, uniaxial stretching with constant width followed by drying in a stretching state was carried out to cellulose hydrogels with physical and chemical double cross-linking networks, achieving high-performance regenerated cellulose films (RCFs) with an impressive tensile strength of 154.5 MPa and an elastic modulus of 5.4 GPa. The hierarchical structure of RCFs during uniaxial stretching and drying was systematically characterized from micro- to nanoscale, including microscopic morphology, crystalline structure as well as relaxation behavior at a molecular level. The two-dimensional correlation spectra of dynamic mechanical analysis and Havriliak-Negami fitting results verified that the enhanced mechanical properties of RCFs were mainly attributed to the stretch-induced tight packing and restricted relaxation of amorphous molecular chains. The new insight concerning the contribution of molecular chains in the amorphous region to the enhancement of mechanical performance for RCFs is expected to provide valuable guidance for designing and fabricating high-performance eco-friendly cellulose-based films.

Tuning egg yolk granules/sodium alginate emulsion gel structure to enhance ß-carotene stability and in vitro digestion property.

In this study, emulsion gels were constructed by ionic gelation method using egg yolk granules/sodium alginate bilayers emulsion. In particular, the main driving force of the emulsion gels was controlled by adjusting pH. Compared with pH 7.0, the mechanical properties of EYGs emulsion gel were enhanced at pH 4.0 (G' > G″). The interfacial protein aggregation that occurred at pH 4.0 promoted the compactness of the EYGs emulsion gel structure along with enhanced capillary effect. The emulsion gel structure tended to be complete at 1 % SA of pH 4.0, for the electrostatic interaction required more SA molecules involved in maintaining emulsion gel structural stability. The denser emulsion gel structure of pH 4.0 than pH 7.0 improved storage stability, FFA releasing, and chemical stability of ß-carotenes. Bioaccessibility of ß-carotenes also decreased to achieve sustained release. This study provides a theoretical basis for tuning emulsion gel structure to adjust encapsulation stability and in vitro digestion characteristics of active ingredients.

Effect of the Graphene Quantum Dot Content on the Thermal, Dynamic-Mechanical, and Morphological Properties of Epoxy Resin.

Different amounts of graphene quantum dots (CQDs) (0, 1, 2.5, and 5 wt%) were incorporated into an epoxy matrix. The thermal conductivity, density, morphology, and dynamic mechanical thermal (DMTA) properties were reused from the study of Seibert et al.. The Pearson plot showed a high correlation between mass loading, thermal conductivity, and thermal diffusivity. A poorer correlation with density and heat capacity was observed. At lower CQD concentrations (0.1 wt%), the fracture surface showed to be more heterogeneous, while at higher amounts (2.5 and 5 wt%), a more homogeneous surface was observed. The storage modulus values did not change with the CQD amount. But the extension of the glassy plateau increased with higher CQD contents, with an increase of ~40 °C for the 5 wt% compared to the 2.5 wt% and almost twice compared to the neat epoxy. This result is attributed to the intrinsic characteristics of the filler. Additionally, lower energy dissipation and a higher glass transition temperature were observed with the CQD amount. The novelty and importance are related to the fact that for more rigid matrices (corroborated with the literature), the mechanical properties did not change, because the polymer bridging mechanism was not present, in spite of the excellent CQD dispersion as well as the filler amount. On the other hand, thermal conductivity is directly related to particle size and dispersion.

Synthesis, Thermal Behavior, and Mechanical Properties of Fully Biobased Poly(Hexamethylene 2,5-Furandicarboxylate-Co-Sebacate) Copolyesters.

In this research, three fully biobased poly(hexamethylene 2,5-furandicarboxylate-co-sebacate) (PHFSe) copolyesters with low contents of hexamethylene sebacate (HSe) unit (10 mol%, 20 mol%, and 30 mol%) were successfully synthesized through a two-step transesterification/esterification and polycondensation method. The chemical structure and actual composition of PHFSe copolyesters were confirmed by hydrogen nuclear magnetic resonance. The thermal behavior and mechanical property of PHFSe copolyesters were investigated and compared with those of the poly(hexamethylene 2,5-furandicarboxylate) (PHF) homopolymer. Both PHFSe copolyesters and PHF showed the high thermal stability. The basic thermal parameters, including glass transition temperature, melting temperature, and equilibrium melting temperature, gradually decreased with increasing the HSe unit content. PHFSe copolyesters crystallized more slowly than PHF under both the nonisothermal and isothermal melt crystallization conditions; however, they crystallized through the same crystallization mechanism and crystal structure. In addition, the mechanical property, especially the elongation at break of PHFSe copolyesters, was obviously improved when the HSe unit content was greater than 10 mol%. In brief, the thermal and mechanical properties of PHF may be easily tuned by changing the HSe unit content to meet various practical end-use requirements.

A biaxially stretched cellulose film prepared from ionic liquid solution.

A biaxially stretched cellulose film with high performance was manufactured from ionic liquid solution through an environmentally friendly, cost effective and facile process. As the transverse stretching ratio (TSR) is increased, the tensile strength and elastic modulus of the biaxially stretched cellulose film in transverse direction (TD) are significantly improved and the coefficient of thermal expansion in TD is reduced while the performance achieves balance in the machine direction (MD) and TD. The transverse stretching regulates the microfibril orientation in the gel film from dominantly uniaxial orientation in MD to homogeneous planar orientation. This microfibril orientation may further play a role in the orientation of the chains in the films during gel drying as evidenced from the birefringence and 2D XRD results. These results indicate cellulose film prepared from ionic liquid process could be utilized with improved structural and mechanical properties by biaxial stretching, and thus serves in various applications.

Physicochemical Properties and In Vitro Biocompatibility of Three Bacterial Nanocellulose Conduits for Blood Vessel Applications.

A novel design of bioreactor G-BNC, in combination with two previously reported designs of bioreactor were used to fabricate three small caliber bacterial nanocellulose (BNC) conduits (G-BNC, S-BNC and D-BNC). They were compared systematically with a clinically-used ePTFE graft. S-BNC possessed a laminated structure, the lowest BNC content, roughest luminal surface and weakest mechanical properties, and so might not be sufficiently strong for use as an artificial blood vessel alone. The D-BNC conduit possessed an unstratified structure with a fiber network that was more dense and the greatest BNC content, providing the strongest mechanical properties. G-BNC possessed a looser network with the smoothest luminal surface and greater hemocompatibility. Following comprehensive evaluation of mechanical properties and performance, we judge that D-BNC and G-BNC should possess greater potential in application as small caliber vascular grafts, however the patency of the three BNC conduits need be further verified in animal studies in vivo.

Anisotropic Compressive Behavior of Metallic Foams under Extreme Temperature Conditions.

Metallic foams find their applicability in complex systems that operate under both real-life conditions (Earth living conditions) and extreme temperature conditions (low or high temperatures). In this paper, the main mechanical properties of closed-cell aluminum alloy (A356) foams under quasi-static compression loading conditions were determined. In order to investigate the compressive behavior, three orthogonal directions (X, Y, and Z) and three testing temperatures (-196, 25 and 250 °C) were considered. It has been observed that the temperature significantly influences the strength properties and energy absorption performances of the aluminum metallic foams AMFs. Moreover, it was found that microstructural characteristics, such as intrinsic defects (intracellular cavities, micro-pores and thin cell-walls) and structural anisotropy (shape, size and orientation of cells), play a decisive role in the mechanical behavior of AMFs. Moreover, the paper compares the relative percentage change (relative percentage increase and decrease) of the main normalized compressive properties (yield stress, plateau stress, densification stress and the energy absorption) of AMF samples, according to testing temperature and loading direction.

The Effect of Concentration of Lithium Salt on the Structural and Transport Properties of Ionic Liquid-Based Electrolytes.

Ionic liquids (ILs) are used as electrolytes in high-performance lithium-ion batteries, which can effectively improve battery safety and energy storage capacity. All atom molecular dynamics simulation and experiment were combined to investigate the effect of the concentration of lithium salt on the performance of electrolytes of four IL solvents ([C n mim][TFSI] and [C n mim][FSI], n = 2, 4). The IL electrolytes exhibit higher density and viscosity; meanwhile, larger lithium ion transfer numbers as the concentration of LiTFSI increases. Furthermore, in order to explore the effect of the concentration of lithium salt on the ionic associations of Li+ and anion of IL, the microstructures of the lithium salt in various IL electrolytes at different concentrations were investigated. The structural analysis indicated that strong bidentate and monodentate coordination was found between Li+ and anion of all IL electrolytes. Both cis and trans isomerism of [FSI]- were observed in [FSI]--type IL electrolyte systems. Furthermore, the existence of the ion cluster [Li[anion] x ](x-1)- in IL electrolytes and the cluster became more closed and compact as the concentration of LiTFSI increases.

In silico properties characterization of water-soluble γ-cyclodextrin bi-capped C60 complex: free energy and geometrical insights for stability and solubility.

Cyclodextrin-related host-guest encapsulation is pivotal to modulate the solubility of C60, thereby promoting its potential therapeutic applications. Here we present a computational study on γ-cyclodextrin bi-capped C60 complex, probing characteristics for all the possible stoichiometry in aqueous solution. The potential of mean force (PMF) delineating the association process was computed, while the geometrical features of corresponding thermodynamically-favored stoichiometry are captured by molecular dynamics simulations, which provides insightful explanations to previous experimental and computational results. PMF partitioning indicates that intermolecular van der Waals dispersion forces are essential for molecular recognition and self-assembly, and the hydrogen-bonding interactions play a key role in dissolving the complex in water.

Crystal-site engineering control for the reduction of Eu(3+) to Eu(2+) in CaYAlO4: structure refinement and tunable emission properties.

In this article, Eu-activated CaYAlO4 aluminate phosphors were synthesized by a solid-state reaction. Under UV light excitation, characteristic red line emission of Eu(3+) was detected in the range of 570-650 nm. In addition, we introduced crystal-site engineering approach into the CaYAlO4 host through incorporation of Si(4+)-Ca(2+) to replace Al(3+)-Y(3+), which would shrink the AlO6 octahedrons, accompanied by the expansion of CaO9 polyhedron, and then enable the partial reduction of Eu(3+) to Eu(2+). The crystal structure and underlying mechanism have been clarified on the basis of the Rietveld refinement analysis. The PL spectra of Ca0.99+xY1-xAl1-xSixO4:Eu0.01 (x = 0-0.30) exhibit both green emission of Eu(2+) (4f(6)5d(1)-4f(7), broadband around 503 nm) and red-orange emission of Eu(3+) ((5)D0-(7)F1,2, 593 and 624 nm) under UV light excitation with a quantum yield of 38.5%. The CIE coordinates of Ca0.99+xY1-xAl1-xSixO4:Eu0.01 (x = 0-0.30) phosphors are regularly shifted from (0.482, 0.341) to (0.223, 0.457) with increasing x, which would expand the application of Eu. Furthermore, this investigation reveals the correlations of structure and property of luminescent materials, which would shed light on the development of novel phosphors suitable for lighting and display applications.