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Covalent Bonds01:29

Covalent Bonds

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When two atoms share electrons to complete their valence shells, they create a covalent bond. An atom's electronegativity—the force with which shared electrons are pulled towards an atom—determines how the electrons are shared. Molecules formed with covalent bonds can be either polar or nonpolar. Atoms with similar electronegativities form nonpolar covalent bonds; the electrons are shared equally. Atoms with different electronegativities share electrons unequally,...
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Network covalent solids contain a three-dimensional network of covalently bonded atoms as found in the crystal structures of nonmetals like diamond, graphite, silicon, and some covalent compounds, such as silicon dioxide (sand) and silicon carbide (carborundum, the abrasive on sandpaper). Many minerals have networks of covalent bonds.
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Proteins can undergo many types of post-translational modifications, often in response to changes in their environment. These modifications play an important role in the function and stability of these proteins. Covalently linked molecules include functional groups, such as methyl, acetyl, and phosphate groups, and also small proteins, such as ubiquitin. There are around 200 different types of covalent regulators that have been identified.
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Compared to ionic bonds, which results from the transfer of electrons between metallic and nonmetallic atoms, covalent bonds result from the mutual attraction of atoms for a “shared” pair of electrons.
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科学领域:

  • 材料科学
  • 纳米技术
  • 催化剂

背景情况:

  • 共价有机框架 (COF) 提供了强大的结构,低密度和高表面积,适用于各种应用.
  • 通常,COF具有微孔性,限制了某些应用的质量传输.
  • 将微孔和宏孔结合在一起的等级孔结构是增强质量传输的理想选择.

研究的目的:

  • 开发一种用于制造具有固有的微度和可调节的宏度的晶体COF的简单策略.
  • 合成和描述具有相互连接的宏微孔结构的基于β-胺的COF.
  • 为了研究氧化演化反应 (OER) 的金属协调层次COF的催化活性.

主要方法:

  • 使用模板诱导方法制造晶体COF,以创建层次的孔隙结构.
  • 在COF骨干中纳入双基,以实现金属协调.
  • 通过在等级孔结构中协调Co2+来合成宏-TpBpy-Co.

主要成果:

  • 成功合成了各种基于β-基因胺的COF与相互连接的宏微孔结构.
  • 合成的巨孔COF保持了高晶度和高的特定表面积.
  • 与纯微孔的COF相比,由此产生的宏TpBpy-Co显著提高了OER活性 (380 mV在10 mA/cm2).

结论:

  • 开发的简单策略可以制造具有可调节的等级孔结构的晶体COF.
  • 在COF中等级的多孔性增强了质量传输特性,这对于催化应用至关重要.
  • 宏观TpBpy-Co催化剂表现出高OER活性,这是由于改善了大规模扩散和可访问的活性点.