Covalent Organic Frameworks (COFs) are promising in the field of photonic energy conversion. However, most efforts have been concentrated on the design of ligand geometric structures and chemical bonding relationships, while understanding the impact of stacking methods on photonic energy conversion remains a significant challenge. In this work, four COFs (1D‐COF, 1D‐MeCOF, 1D‐tBuCOF and 2D‐COF) with the same main‐chain structure but different stacking methods are designed and synthesized, using photocatalytic hydrogen evolution as a model reaction. Mortise‐tenon stacked 1D‐MeCOF exhibits far superior photocatalytic hydrogen evolution performance to other stacking methods, and it maintains high efficiency and stability in natural seawater systems. Extensive characterization demonstrates that such a unique mortise‐tenon stacking structure of 1D‐MeCOF inhibits interchain slippage, enhances π‐stacking, and maximizing light absorption capabilities. Furthermore, unidirectional carrier transport characteristics of one‐dimensional structure can generate a strong photo‐induced self‐built electric field, which acts as "self‐catalysis" to accelerate carrier transport. This work provides an effective design strategy and mechanistic insights on the stacking engineering of photonic energy conversion materials.
Methyl transfer reactions are of great significance in the field of synthetic chemistry and life sciences.So far, most of the reported methyl migration reactions have occurred between different types of molecules.Therefore, it is of certain value to search for new methyl transfer reactions.In this study, fenthion, a most common insecticide in the environment, was selected as the studied object, and electrospray ionization mass spectrometry (ESI-MS) was used as the analytical tool to conduct highly sensitive analysis of the reaction system, so as to explore the possibility of methyl transfer reaction in fenthion molecules under the condition of trifluoroacetic acid and nanometer titanium dioxide.Other than m/z 279 (protonated fenthion), some new product ions (m/z 293 and m/z 265) could be observed in the fingerprint MS of fenthion reaction solution.Tandem MS experiments showed that the intensity of product ion m/z 231 (elimination of CH 3 SH) in the dissociation of m/z 279 from fenthion reaction solution were different from that from protonated fenthion standard.This indicated that the methyl in the fenthion could transfer from oxygen atom to unsaturated sulfur atom via 1,3-methyl transfer, forming isomer a2, which led to the high intensity of product ion m/z 231 in the dissociation of m/z 279 from fenthion reaction solution.Under the assistance of acid, the methyl cation continued to transfer from sulfur atom in a2 to the unsaturated sulfur atom in another fenthion molecule, forming a3 (m/z 293) and a4 via intermolecular methyl transfer reaction, which was verified by tandem MS experiments of ions at m/z 293 and m/z 265.In addition, density functional theory (DFT) calculations were carried out to confirm the mechanism of intramolecular and intermolecular methyl transfer reactions of fenthion.In order to observe the phenomenon of methyl transfer more intuitively, the effects of different acids, metal oxides, reaction time and reaction temperature on the signal intensities of ions at m/z 265 and m/z 293 of intermolecular methyl transfer reactions of fenthion were investigated.It could be concluded that under the conditions of trifluoroacetic acid and nanometer titanium dioxide, and 60 ℃ ultrasound reaction for 6 h, the proportion of intermolecular methyl transfer reactions of fenthion was the highest.In
A lithiophilic Co/Co4N-N-doped carbon electrode displays a high coulombic efficiency (98.5%) and dendrite-free morphology for long-life Li–air batteries.
The unique dual role of zinc atoms in a novel layered mixed zinc–vanadium phosphate has been shown by X-ray crystallography to consist of Zn/V/P/O inorganic anionic layers with cationic complex fragments in pairs attached perpendicularly to the layers.
The combination of ferroelectric–optical properties in halide perovskites has attracted tremendous interess because of its potential for optoelectronic and energy applications. However, very few reports focus on the ferroelectricity of all-inorganic halide perovskites quantum dots. Herein, we report a excellent ferroelectricity in CsPbBr3 quantum dots (QDs) with a saturation polarization of 0.25 μC/cm2. Differential scanning calorimetry, X-ray diffraction, and transmission electronic microscopy revealed that the mechanism of ferroelectric–paraelectric switching of CsPbBr3 QDs can be attributed to the phase transition from cubic phase (Pm3̅m) to the orthorhombic phase (Pna21). In the orthorhombic CsPbBr3, the distortion of octahedral [PbBr6]4– structural units and the off-center Cs+ generated the slightly separated centers of positive charge and negative charge, resulting in the ferroelectric properties. The variable-temperature emission spectrum from 328 to 78 K exhibits green luminescence and a gradual red shift due to the phase transition. This finding opens up an avenue to explore the ferroelectric–optical properties of inorganolead halide perovskites for high-performance multifunctional materials.
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