Ultrathin metasurface compromising various sub-wavelength meta-particles offers promising advantages in controlling electromagnetic wave by spatially manipulating the wavefront characteristics across the interface. The recently proposed digital coding metasurface could even simplify the design and optimization procedures due to the digitalization of the meta-particle geometry. However, current attempts to implement the digital metasurface still utilize several structural meta-particles to obtain certain electromagnetic responses, and requiring time-consuming optimization especially in multi-bits coding designs. In this regard, we present herein utilizing geometric phase based single structured meta-particle with various orientations to achieve either 1-bit or multi-bits digital metasurface. Particular electromagnetic wave scattering patterns dependent on the incident polarizations can be tailored by the encoded metasurfaces with regular sequences. On the contrast, polarization insensitive diffusion-like scattering can also been successfully achieved by digital metasurface encoded with randomly distributed coding sequences leading to substantial suppression of backward scattering in a broadband microwave frequency. The proposed digital metasurfaces provide simple designs and reveal new opportunities for controlling electromagnetic wave scattering with or without polarization dependence.
Two-dimensional
(2D) metallic transition metal dichalcogenides
(MTMDCs) have attracted tremendous interest due to their intriguing
physical properties and broad application potential. However, batch
production of high-quality 2D MTMDCs based on existing synthesis on
2D surfaces remains a huge challenge. Herein, a universal synthetic
route for the scalable synthesis of high-quality 2D MTMDC (e.g., TaS2, V5S8, and NbS2) nanosheets
using microcrystalline NaCl crystals as templates via a facile chemical
vapor deposition method is reported. Obviously, this synthetic route
is perfectly compatible with a facile water dissolution–filtration
process for obtaining high-purity MTMDC nanosheet powders. Representatively,
a thickness-uniform 1T-TaS2 nanosheet product can be achieved
that shows unexceptionable dispersibility in ethanol, which allows
its assembly onto arbitrary substrates/electrodes for high-performance
energy-related applications, herein serving as a high-performance
electrocatalyst for the hydrogen evolution reaction. This work sheds
light on the batch production, green transfer, and energy-related
application of 2D MTMDC materials.
CO2 cycloaddition with epoxides at low temperature and pressure has been broadly recognized as an ambitious but challenging goal, which requires the catalysts to have precisely controlled Lewis acid sites. Here, we demonstrate that both stereochemical environment and oxidation state of single cobalt active sites in cobalt tetraaminophthalocyanine [CoPc(NH2)4] are finely tuned via molecular engineering with 2,5-di-tert-butyl-1,4-benzoquinone (DTBBQ). Notably, DTBBQ incorporation not only enables formation of 5-nm-thick conjugated microporous polymer (CMP) nanosheets due to the steric hindrance effect of tert-butyl groups but also makes isolated cobalt sites with high oxidation state due to the presence of delocalized electron-withdrawing effect of alkene groups in DTBBQ via conjugated skeleton. Notably, when used as heterogeneous catalysts for CO2 cycloaddition with different epoxides, single cobalt active sites on the ultrathin CMP nanosheets exhibit unprecedentedly high activity and excellent stability under mild reaction conditions.
Covalent organic frameworks (COFs) have emerged as a fascinating crystalline porous material and are widely used in the field of catalysis. However, developing simple approaches to fabricate conjugated COFs with specific functional groups remains a significant challenge. In this study, the construction of defective COF‐LZU1 with Lewis acid sites embedded into the frameworks is fulfilled by a facile solvent‐assisted ligand exchange method. A monodentate ligand, protocatechualdehyde, is successfully introduced into the skeleton of COF‐LZU1, which endows the defects in the structure of COF‐LZU1 via replacement of the original coordinated benzene‐1,3,5‐tricarbaldehyde ligand. As‐synthesized defective COF‐LZU1 decorated with protocatechualdehyde is rich of free hydroxy groups for chelating with active metal ions. Specifically, after combining with Fe3+, the defective COF‐LZU1 shows excellent activity in catalytic alcoholysis of epoxides under mild conditions. The method reported here will open up the opportunity to incorporate different functional groups into COFs and enrich the strategies for creating new types of porous catalysts.
Alloying degree of PtRu bimetallic nanoparticles can be controlled to finely tune electronic effect for enhanced Hydrogen oxidation reaction in alkaline.
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