Antimonene fabricated by mechanical exfoliation is highly stable under atmospheric conditions over periods of months and even when immersed in water. Density functional theory confirms the ...experiments and predicts an electronic gap of ≈1 eV. These results highlight the use of antimonene for optoelectronics applications.
The use of covalent organic frameworks (COFs) in practical applications demands shaping them into macroscopic objects, which remains challenging. Herein, we report a simple three‐step method to ...produce COF aerogels, based on sol‐gel transition, solvent‐exchange, and supercritical CO2 drying, in which 2D imine‐based COF sheets link together to form hierarchical porous structures. The resultant COF aerogel monoliths have extremely low densities (ca. 0.02 g cm−3), high porosity (total porosity values of ca. 99 %), and mechanically behave as elastic materials under a moderate strain (<25–35 %) but become plastic under greater strain. Moreover, these COF aerogels maintain the micro‐ and meso‐porosity of their constituent COFs, and show excellent absorption capacity (e.g. toluene uptake: 32 g g−1), with high removal efficiency (ca. 99 %). The same three‐step method can be used to create functional composites of these COF aerogels with nanomaterials.
A three‐step method produces COF aerogel monoliths, based on sol–gel transition, solvent‐exchange, and supercritical CO2 drying. 2D imine‐based COF sheets link together to form hierarchical porous structures. The aerogels have extremely low densities, high porosity, and mechanically behave as elastic or plastic materials under different strain. They show excellent absorption capacity with high removal efficiency.
Abstract Covalent organic frameworks (COFs) have witnessed outstanding developments in the past 15 years, particularly in optimizing their pore structures, linkages, and variety of monomers used in ...their synthesis. Yet, a significant challenge remains unaddressed: the processability of COFs into macroscopic architectures with arbitrary shapes, as they are typically obtained as unprocessable powders. This study presents a novel strategy to address this issue by developing a 3D printable ink comprising a colloidal water suspension of COF nanoparticles. A microfluidic device is engineered that provides precise control over the gelation process of the COF‐based ink, allowing for a layer‐by‐layer fabrication. As a result, the direct production of large‐scale binder‐free COF architectures from digital designs is achieved at room temperature and atmospheric pressure while eliminating the use of toxic organic solvents.
2D materials have opened a new field in materials science with outstanding scientific and technological impact. A largely explored route for the preparation of 2D materials is the exfoliation of ...layered crystals with weak forces between their layers. However, its application to covalent crystals remains elusive. Herein, a further step is taken by introducing the exfoliation of germanium, a narrow‐bandgap semiconductor presenting a 3D diamond‐like structure with strong covalent bonds. Pure α‐germanium is exfoliated following a simple one‐step procedure assisted by wet ball‐milling, allowing gram‐scale fabrication of high‐quality layers with large lateral dimensions and nanometer thicknesses. The generated flakes are thoroughly characterized by different techniques, giving evidence that the new 2D material exhibits bandgaps that depend on both the crystallographic direction and the number of layers. Besides potential technological applications, this work is also of interest for the search of 2D materials with new properties.
α‐Germanium crystals are exfoliated using a wet ball‐milling technique to produce α‐germanium nanolayers (α‐Ge NLs) in a process that is upscaled to gram production. The α‐Ge NLs can be redispersed using a shear‐mixer, yielding very stable suspensions. Theoretical calculations predict a thickness‐dependent bandgap of these NLs that is confirmed by electron energy‐loss spectroscopy of α‐Ge NLs with different orientations.
Abstract In this study, we present a novel approach for the synthesis of covalent organic frameworks (COFs) that overcomes the common limitations of non‐scalable solvothermal procedures. Our method ...allows for the room‐temperature and scalable synthesis of a highly fluorinated DFTAPB‐TFTA‐COF, which exhibits intrinsic hydrophobicity. We used DFT‐based calculations to elucidate the role of the fluorine atoms in enhancing the crystallinity of the material through corrugation effects, resulting in maximized interlayer interactions, as disclosed both from PXRD structural resolution and theoretical simulations. We further investigated the electrocatalytic properties of this material towards the oxygen reduction reaction (ORR). Our results show that the fluorinated COF produces hydrogen peroxide selectively with low overpotential (0.062 V) and high turnover frequency (0.0757 s −1 ) without the addition of any conductive additives. These values are among the best reported for non‐pyrolyzed and metal‐free electrocatalysts. Finally, we employed DFT‐based calculations to analyse the reaction mechanism, highlighting the crucial role of the fluorine atom in the active site assembly. Our findings shed light on the potential of fluorinated COFs as promising electrocatalysts for the ORR, as well as their potential applications in other fields.
Covalent organic frameworks (COFs) are crystalline materials with intrinsic porosity that offer a wide range of potential applications spanning diverse fields. Yet, the main goal in the COF research ...area is to achieve the most stable thermodynamic product while simultaneously targeting the desired size and structure crucial for enabling specific functions. While significant progress is made in the synthesis and processing of 2D COFs, the development of processable 3D COF nanocrystals remains challenging. Here, a water‐based nanoreactor technology for producing processable sub‐40 nm 3D COF nanoparticles at ambient conditions is presented. Significantly, this technology not only improves the processability of the synthesized 3D COF, but also unveils exciting possibilities for their utilization in previously unexplored domains, such as nano/microrobotics and biomedicine, which are limited by larger crystallites.
Herein, a water‐based nanoreactor technology that allows for the controlled generation of sub‐40 nm 3D covalent organic frameworks (COF) nanoparticles, boosting processability, and opening new frontiers in nano/microrobotics and biomedicine is presented. This breakthrough clearly overcomes the limitations posed by larger reported 3D COF crystal structures, unlocking exciting possibilities for previously unexplored domains.
To date, crystallization studies conducted in space laboratories, which are prohibitively costly and unsuitable to most research laboratories, have shown the valuable effects of microgravity during ...crystal growth and morphogenesis. Herein, an easy and highly efficient method is shown to achieve space‐like experimentation conditions on Earth employing custom‐made microfluidic devices to fabricate 2D porous crystalline molecular frameworks. It is confirmed that experimentation under these simulated microgravity conditions has unprecedented effects on the orientation, compactness and crack‐free generation of 2D porous crystalline molecular frameworks as well as in their integration and crystal morphogenesis. It is believed that this work will provide a new “playground” to chemists, physicists, and materials scientists that desire to process unprecedented 2D functional materials and devices.
How to achieve simulated microgravity conditions on Earth? The art of growing and processing 2D porous crystalline molecular frameworks in simulated microgravity is presented.
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