Latest ArticlesSelective oxidation of olefin to epoxides is an important reaction in industry, however, developing heterogeneous catalysts to achieve the effective catalysis for this reaction under O2 atmosphere at room temperature is challenging but highly desired. In this work, two novel 2D cobalt metal-organic complexes, namely [Co(L)(5-HIP)]·2H2O (Co-MOC-1) and [Co(L)(BTEC)0.5]·H2O (Co-MOC-2) (L = (E)-4,4′-(ethene-1,2-diyl)bis(N-(pyridin-3-yl)benzamide; 5-H2HIP = 5-hydroxyisophthalic acid; H4BTEC = pyromellitic acid) were designed and synthesized through hydrothermal method, which exhibited different metal coordination modes (4-coordinate and 5-coordinate, respectively) and 2D layer structures directed by different carboxylates co-ligands. Two Co-MOCs can serve as heterogeneous catalysts for the selective oxidation of olefins to epoxides at room temperature using O2 as oxidant. Furthermore, a higher catalysis activity of Co-MOC-1 than Co-MOC-2 (96.7% vs. 90.2% yield of 1,2-epoxycyclooctane) was observed, which may be attributed to the coordination unsaturated Co centers, the less coordination number and larger interlayer spacing of Co-MOC-1.
Metal-organic framework (MOF) has been widely applied in photocatalysis, which is significant for addressing energy crises and environmental issues. Based on density functional theory calculations, the performances of Cu-BTC, a copper-based MOF, and its derivatives CuTM-BTC via the substitution of transition metal (TM) elements at the Cu site for photocatalytic overall water splitting (POWS) have been studied. POWS of Cu-BTC suffers from the sluggish hydrogen evolution reaction due to the large overpotential of 2.02 V and limited solar utilization due to a wide HOMO-LUMO gap of 4.11 eV. Via TM substitution, the HOMO-LUMO gap narrows but still satisfies the redox potentials when taken 3d-TM of Cr, Fe, Co or Ni, 4d-TM of Rh or Pd, or 5d-TM of Re or Pt into consideration, benefiting for the light absorption. Furthermore, Cr and Re could serve as active sites for hydrogen evolution with remarkably lowered overpotentials of 0.79 V and 0.28 V, respectively; similarly, oxygen evolution activities could be enhanced by Fe, Co and Rh because of their reduced overpotentials which are less than 0.5 V. Therefore, our findings pave guidance for designing Cu-BTC derivatives in overall water splitting.
Sulfates are always promising short-wave ultraviolet (UV) nonlinear optical (NLO) candidates, if their birefringence could be greatly improved. Here, in terms of the insufficient birefringence, the unity of heteroleptic tetrahedral groups and triangular ones was proposed and implemented. Thus, a new semi-organic crystal, [C(NH2)3]S3O6 (G2S3O6), was obtained, which is composed of [S3O6]2− and [C(NH2)3]+ groups. It exhibits excellent optical properties with a short absorption cutoff edge of 218 nm, a strong NLO response of 1.4 × KH2PO4, and more especially, a large birefringence of 0.097@546 nm. This birefringence leap makes the G2S3O6 crystal achieve a phase-matching behavior under a 532 nm laser. Thus, the synergy of [S3O6]2− and [C(NH2)3]+ groups results in excellent optical performances. This finding opens a new horizon for exploring novel UV NLO crystals.
Carbon materials are considered as prospective anode candidates for potassium ion batteries (PIBs). However, the low-rate capability is hampered by slow K+ diffusion kinetics and obstructed electron transport of carbon-based anodes. In this work, calcium d-gluconate derived mesoporous carbon nanosheets (CGC) were interpenetrated into the architecture of reduced graphene oxides (RGO) to form the composites of two-dimensional (2D)/2D graphene/mesoporous carbon nanosheets (RGO@CGC). CGC as a rigid skeleton can prevent the graphene layers from restacking and maintain the structural stability of the 2D/2D carbon composites of RGO@CGC. The mesopores in CGC can shorten the path of ion diffusion and facilitate the penetration of electrolytes. RGO possesses the high surface-to-volume ratio and superior electron transport capability in the honeycomb-like 2D network consisting of sp2-hybridized carbon atoms. Especially, the π-π stacking interaction between CGC and RGO enhances stable composite structure formation, expedites interlayer-electron transfer, and establishes three-dimensional (3D) ion transportation pathways. Owing to these unique structure, RGO@CGC exhibits fast and stable potassium storage capability. Furthermore, the effects of binders and electrolytes on the electrochemical performance of RGO@CGC were investigated. Finally, Prussian blue was synthesized as a positive electrode to explore the possibility of RGO@CGC as a full battery application.
Two dimensional (2D) materials based on boron and carbon have attracted wide attention due to their unique properties. BC compounds have rich active sites and diverse chemical coordination, showing great potential in optoelectronic applications. However, due to the limitation of calculation and experimental conditions, it is still a challenging task to predict new 2D BC monolayer materials. Specifically, we utilized Crystal Diffusion Variational Autoencoder (CDVAE) and pre-trained Materials Graph Neural Network with 3-Body Interactions (M3GNet) model to generate novel and stable BCP materials. Each crystal structure was treated as a high-dimensional vector, where the encoder extracted lattice information and element coordinates, mapping the high-dimensional data into a low-dimensional latent space. The decoder then reconstructed the latent representation back into the original data space. Additionally, our designed attribute predictor network combined the advantages of dilated convolutions and residual connections, effectively increasing the model's receptive field and learning capacity while maintaining relatively low parameter count and computational complexity. By progressively increasing the dilation rate, the model can capture features at different scales. We used the DFT data set of about 1600 BCP monolayer materials to train the diffusion model, and combined with the pre-trained M3GNet model to screen the best candidate structure. Finally, we used DFT calculations to confirm the stability of the candidate structure. The results show that the combination of generative deep learning model and attribute prediction model can help accelerate the discovery and research of new 2D materials, and provide effective methods for exploring the inverse design of new two-dimensional materials.
Enhancement of the nonlinear optical (NLO) output power of lasers requires urgent development of an NLO crystal with a significant second-harmonic generation (SHG) response and sufficient birefringence for phase-matching capability; however, simultaneously optimizing these two key parameters remains a great challenge. In contrast to traditional single-anion units, the stereochemically-active lone pair Sb3+ ion is coordinated by S2− and I− ions to yield the mixed-anionic SbSI chalcohalide that can enhance hyperpolarizability and anisotropic polarizability concurrently. As anticipated, SbSI exhibited the largest SHG response (5.7 × AgGaS2@1.91 µm) among phase-matching Sb-based sulfides, the favorable laser-induced damage threshold (LIDT, 2.3 × AgGaS2@2.09 µm), and the giant calculated birefringence (0.62@1.91 µm). Structural analysis and computational simulations indicate that the highly polarizable mixed anion determine the enormous SHG response and birefringence.
Metallabenzenes, a type of aromatic compound that includes metal atoms, have opened up new avenues for creating materials with unique properties. A distinctive feature of metallabenzenes is the significant deviation of their metal atoms from the planar configuration of the C5 ring, a phenomenon that paradoxically enhances their aromatic character. In this investigation, we propose that this counterintuitive increase in aromaticity upon geometric distortion is governed by the interactions of frontier orbitals in the σ-space. This insight not only corroborates the previously suggested role of σ-space orbitals in inducing geometric non-planarity in metallabenzenes but also underscores their pivotal contribution to the compounds' enhanced aromaticity. As a result, this work broadens the scope of the σ-control mechanism, highlighting its usefulness for the rational design of functional metalla-aromatic materials.
The Fenton method is an effective technology for the removal of organic materials from wastewater. In this work, an induced catalyst Fe3O4 was synthesized by a hydrothermal method, and the modulation of the chemical composition of Fe3O4 crystals was achieved under the microwave shock method with the same effect as that of calcination treatment. Fe3O4 catalyst for the removal of the dye Rhodamine B (RhB) from polluted wastewater under microwave (MW), H2O2 system. The results showed that Fe3O4 nanomicrospheres prepared by microwave shock exhibited superior catalytic activity under the conditions of 500 W, 0.4 mol/L H2O2 and10 mg/L RhB, and the removal rate of RhB reached 98.5% after 10 min. The Fe3O4 catalysts also exhibited good stability and degradation efficiency. Electron paramagnetic resonance experiments confirmed that •OH plays a major role in the rapid degradation of RhB. Under microwave action, the catalyst produces electron-hole pairs, in which the holes react with OH− produced by water ionisation to form •OH, and the microwave-treated Fe3O4 produces more active species. Fe3+ and Fe2+ serve as microwave catalytic activity centers and Fenton catalytic activity centers, respectively. This research demonstrates that optimizing the Fe2+/Fe3+ ratio significantly enhances the degradation efficiency of RhB. This study presents novel views regarding the mechanism of microwave synergistic catalyst-induced Fenton.
Fluoride-based electrolyte exhibits extraordinarily high oxidative stability in high-voltage lithium metal batteries (h-LMBs) due to the inherent low highest occupied molecular orbital (HOMO) of fluorinated solvents. However, such fascinating properties do not bring long-term cyclability of h-LMBs. One of critical challenges is the interface instability in contacting with the Li metal anode, as fluorinated solvents are highly susceptible to exceptionally reductive metallic Li attributed to its low lowest unoccupied molecular orbital (LUMO), which leads to significant consumption of the fluorinated components upon cycling. Herein, attenuating reductive decomposition of fluorinated electrolytes is proposed to circumvent rapid electrolyte consumption. Specifically, the vinylene carbonate (VC) is selected to tame the reduction decomposition by preferentially forming protective layer on the Li anode. This work, experimentally and computationally, demonstrates the importance of pre-passivation of Li metal anodes at high voltage to attenuate the decomposition of fluoroethylene carbonate (FEC). It is expected to enrich the understanding of how VC attenuate the reactivity of FEC, thereby extending the cycle life of fluorinated electrolytes in high-voltage Li-metal batteries.
Constructing high-performance electrocatalysts for oxygen evolution reaction (OER) using a simple and economical strategy is considerably meaningful yet still challenging. Herein, Co(OH)2/Mo2TiC2Tx (where T represents the surface functional groups, -O, -OH and -F) hetero-nanosheets were facilely prepared by the in situ topochemical transformation at room temperature towards efficient OER. The integrity of Co(OH)2 nanosheets and Mo2TiC2Tx nanosheets affords interfacial coupling to optimize the electronic structures of Co and Mo ions, which endows the high electron transfer efficiency and rapid reaction kinetics. As a result, the Co(OH)2/Mo2TiC2Tx hetero-nanosheets exhibit excellent OER performances with low overpotentials of 283 mV on glass-carbon electrode, and 227 mV on nickel foam at 10 mA/cm2. Furthermore, the decent anti-alkali ability underpins superior operational stability exceeding 100 h, demonstrating grand potential in practical applications. This work provides a new insight for the synthesis of efficient and cost-effective two-dimensional (2D) material-based electrocatalysts.
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