4-Methyl-5-vinyl thiazole modified Ni-MOF/g-C3N4/CdS composites for efficient photocatalytic hydrogen evolution without precious metal cocatalysts.

The construction of heterojunction systems is an effective way to efficiently generate hydrogen by water photolysis. In this work, Ni-MOF (trimesic acid, (BTC)) and g-C3N4 (denoted as CN) were combined, and then Ni-MOF/CN was modified by 4-Methyl-5-vinyl thiazole (denoted as MVTh). Finally, CdS was loaded on the surface of Ni-MOF/CN/MVTh to prepare the photocatalyst Ni-MOF/g-C3N4/MVTh/CdS (denoted as Ni/CN/M/Cd) with a triangular closed-loop path heterojunction for the first time. As a photocatalyst without precious metal cocatalysts, Ni/CN/M/Cd displayed high H2 evolution (17.844 mmol·g-1·h-1) under an optimum CdS loading of 40 wt%. The H2 evolution rate was approximately 79 times that of Ni-MOF/CN and exceeded those of almost all catalysts based on MOF/CN in the literature. The triangular closed-loop heterojunction formed between Ni-MOF, g-C3N4, and CdS could realize the directional migration of photocarriers and significantly diminished the transfer resistance of carriers. The Ni2+ in Ni-MOF provided many cocatalytic sites for H2 evolution via g-C3N4 and CdS. Furthermore, charge carrier separation in Ni-MOF/CN/CdS improved after the innovative addition of MVTh. This study provides a reference for the construction of a closed-loop heterojunction system without precious metal cocatalysts.

Comment on "Cryoforged nanotwinned titanium with ultrahigh strength and ductility".

We analyze the results of Zhao et al. (Reports, 17 September 2021, p. 1363) with a focus on the mechanical properties and microstructural evolution. We conclude that their results, together with the explanations and interpretations, are confusing, misleading, or even wrong.

Application of a novel biomimetic double-ligand zirconium-based metal organic framework in environmental restoration and energy conversion.

The development of visible-light response photocatalysts with a high catalytic performance and long-term cyclic stability is of great significance in the field of energy and environmental protection. Inspired by photosynthesis, a novel three-dimensional coral zirconium-based metal organic framework (MOF) was synthesized using a double-ligand strategy. The optimal sample, Zr-TCPP-bpydc (2:1), (the ratio of tetra-(4-carboxyphenyl) porphyrin to 2,2'-bipyridine-5,5'-dicarboxylic acid is 2:1) shows an excellent photocatalytic activity under visible light irradiation, and the effects of the amount of photocatalyst, pH and concentration on the degradation rate were investigated under the optimum conditions. It has a high degradation rate of tetracycline (98.12% for tetracycline and 96.74% for ofloxacin), which is 2.11 times higher than that of single ligand Zr-bpydc (zirconium-based MOF containing only 2,2'-bipyridine-5,5'-dicarboxylic acid). More importantly, it also has a good H2 evolution rate (213.68 µmol g-1h-1) and CO2 reduction (35.81 µmol g-1h-1). In addition, the intermediate pathway of degradation, photocatalytic enhancement mechanism and cycle stability were deeply studied by liquid chromatography-mass spectrometry (LC-MS), electron spin resonance spectroscopy (ESR), linear sweep voltammetry (LSV) and recycling tests. The synthesis of a three-dimensional biomimetic coral zirconium-based MOF material will provide guidance for the development of new, promising, and natural ideal photocatalytic materials.

Flower-Like Dual-Defective Z-Scheme Heterojunction g-C3N4/ZnIn2S4 High-Efficiency Photocatalytic Hydrogen Evolution and Degradation of Mixed Pollutants.

Graphitic carbon nitride (g-C3N4) with a porous nano-structure, nitrogen vacancies, and oxygen-doping was prepared by the calcination method. Then, it was combined with ZnIn2S4 nanosheets containing zinc vacancies to construct a three-dimensional (3D) flower-like Z-scheme heterojunction (pCN-N/ZIS-Z), which was used for photocatalytic hydrogen evolution and the degradation of mixed pollutants. The constructed Z-scheme heterojunction improved the efficiency of photogenerated charges separation and migration, and the large surface area and porous characteristics provided more active sites. Doping and defect engineering can change the bandgap structure to improve the utilization of visible light, and can also capture photogenerated electrons to inhibit recombination, so as to promote the use of photogenerated electron-hole pairs in the photocatalytic redox process. Heterojunction and defect engineering synergized to form a continuous and efficient conductive operation framework, which achieves the hydrogen production of pCN-N/ZIS-Z (9189.8 µmol·h-1·g-1) at 58.9 times that of g-C3N4 (155.9 µmol·h-1·g-1), and the degradation rates of methyl orange and metronidazole in the mixed solution were 98.7% and 92.5%, respectively. Our research provides potential ideas for constructing a green and environmentally friendly Z-scheme heterojunction catalyst based on defect engineering to address the energy crisis and environmental restoration.

Dynamic self-strengthening of a bio-nanostructured armor - conch shell.

Bio-nanowire structured armors - conch shells, which are often collected as art pieces, possess a special function - an unusual resilience against high speed predatory attacks. Under high-strain-rate compression (strain rate ~103 s-1) conch shells highlight significantly high fracture strength vis-à-vis under quasi-static loading (strain rate ≤ 10-2/s). The dynamic fracture strength reaches a strikingly high value of 600 MPa, 67% enhancement with reference to that of quasi-static loading with the fracture strength 360 MPa. Upon dynamic impact loading, conch shells ingeniously activated a new defense mechanism - intra-lamella fracture, which differs from the inter-lamella fracture damage under quasi-static loading. The lengthy third-order lamellae with a length of hundreds of micrometers were pulverized into rods with the length ranging from 0.4 µm and 2.5 µm upon dynamic loading, whereas the third-order lamellae in the quasi-statically fractured segments maintained the length of hundreds of micrometers. Multiple energy-dissipating mechanisms - intra-lamella fracture, nanoparticle rotation and dislocation enabled nanoparticle deformation in a synergistical fashion contribute to the high strain rate fracture strength of conch shells. This dynamic self-strengthening strategy provides a new guideline for designing dynamically robust materials.

Atomistic Origin of Deformation Twinning in Biomineral Aragonite.

Deformation twinning rarely occurs in mineral materials which typically show brittle fracture. Surprisingly, it has recently been observed in the biomineral aragonite phase in nacre under high rate impact loading. In this Letter, the twinning tendency and the competition between fracture and deformation twinning were revealed by first principles calculations. The ratio of the unstable stacking fault energy and the stacking fault energy in orthorhombic aragonite is hitherto the highest in a broad range of metallic and oxide materials. The underlining physics for this high ratio is the multineighbor shared ionic bonds and the unique relaxation process during sliding in the aragonite structure. Overall, the unique deformation twining along with other highly coordinated deformation mechanisms synergistically work in the hierarchical structure of nacre, leading to the remarkable strengthening and toughening of nacre upon dynamic loading, and thus protecting the mother-of-pearl from predatory attacks.

Design and fabrication of a metastable ß-type titanium alloy with ultralow elastic modulus and high strength.

Titanium and its alloys have become the most attractive implant materials due to their high corrosion resistance, excellent biocompatibility and relatively low elastic modulus. However, the current Ti materials used for implant applications exhibit much higher Young's modulus (50 ~ 120 GPa) than human bone (~30 GPa). This large mismatch in the elastic modulus between implant and human bone can lead to so-called "stress shielding effect" and eventual implant failure. Therefore, the development of ß-type Ti alloys with modulus comparable to that of human bone has become an ever more pressing subject in the area of advanced biomedical materials. In this study, an attempt was made to produce a bone-compatible metastable ß-type Ti alloy. By alloying and thermo-mechanical treatment, a metastable ß-type Ti-33Nb-4Sn (wt. %) alloy with ultralow Young's modulus (36 GPa, versus ~30 GPa for human bone) and high ultimate strength (853 MPa) was fabricated. We believe that this method can be applied to developing advanced metastable ß-type titanium alloys for implant applications. Also, this approach can shed light on design and development of novel ß-type titanium alloys with large elastic limit due to their high strength and low elastic modulus.

Uncovering high-strain rate protection mechanism in nacre.

Under high-strain-rate compression (strain rate approximately 10(3) s(-1)), nacre (mother-of-pearl) exhibits surprisingly high fracture strength vis-à-vis under quasi-static loading (strain rate 10(-3) s(-1)). Nevertheless, the underlying mechanism responsible for such sharply different behaviors in these two loading modes remains completely unknown. Here we report a new deformation mechanism, adopted by nacre, the best-ever natural armor material, to protect itself against predatory penetrating impacts. It involves the emission of partial dislocations and the onset of deformation twinning that operate in a well-concerted manner to contribute to the increased high-strain-rate fracture strength of nacre. Our findings unveil that Mother Nature delicately uses an ingenious strain-rate-dependent stiffening mechanism with a purpose to fight against foreign attacks. These findings should serve as critical design guidelines for developing engineered body armor materials.

High Plasticity and Substantial Deformation in Nanocrystalline NiFe Alloys Under Dynamic Loading.

A nanocrystalline (NC) NiFe alloy is presented, in which both highly improved plasticity and strength are achieved by the dynamic-loading-induced deformation mechanisms of de-twinning (that is, reduction of twin density) and significant grain coarsening. This work highlights potential ingenious avenues to exploit the superior behavior of NC materials under extreme conditions.