2D Covalent Organic Frameworks with cem Topology.
Xuan Wang1, Xing Han1, Cheng Cheng1
1School of Chemistry and Chemical Engineering, Frontiers Science Center for Transformative Molecules and State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240, China.
Journal of the American Chemical Society
|April 14, 2022
Summary
Researchers created novel 2D porous covalent organic frameworks (COFs) with a unique cem topology. These materials demonstrate excellent performance in separating environmental pollutants using high-performance liquid chromatography (HPLC).
Area of Science:
- Materials Science
- Nanotechnology
- Chemistry
Background:
- Two-dimensional (2D) layered covalent organic frameworks (COFs) are widely studied.
- Existing COF topologies are limited to seven known structures due to restricted building blocks.
- Novel network structures are needed to expand the properties and applications of COFs.
Purpose of the Study:
- To synthesize 2D porous COFs with unprecedented network topologies.
- To explore the use of pseudo-fivefold symmetric building blocks for COF construction.
- To evaluate the performance of these new COFs in separating polycyclic aromatic hydrocarbons (PAHs).
Main Methods:
- Dynamic imine bond formation linking 1,2,3,4,5-penta(4-formylphenyl)pyrrole with linear aromatic diamines.
- Characterization of the resulting three-dimensional (3D) porous COFs.
- High-performance liquid chromatography (HPLC) column packing and separation analysis.
Main Results:
- Three isostructural 2D porous COFs with a novel cem topology were successfully synthesized.
- These COFs exhibit an eclipsed stacking structure with unidirectional hierarchical pores.
- The COF-packed HPLC columns demonstrated excellent separation of 10 different polycyclic aromatic hydrocarbons (PAHs).
Conclusions:
- The study introduces the first five-vertex semiregular Archimedean tessellations in COFs, expanding known topologies.
- The developed COFs possess high thermal and chemical resistance, suitable for demanding applications.
- This work provides a new strategy for designing COFs with novel topologies and enhanced properties, particularly for environmental pollutant separation.
Related Concept Videos
02:46Crystal Field Theory - Tetrahedral and Square Planar Complexes
45.0K
Tetrahedral Complexes
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
45.0K
02:58Crystal Field Theory - Octahedral Complexes
28.1K
Crystal Field Theory
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
28.1K
01:18Aromatic Hydrocarbon Cations: Structural Overview
3.1K
Cycloheptatriene is a neutral monocyclic unsaturated hydrocarbon that consists of an odd number of carbon atoms and an intervening sp3 carbon in the ring. The three double bonds in the ring correspond to 6 π electrons, which is a Huckel number, and therefore satisfies the criteria of 4n + 2 π electrons. However, the intervening sp3 carbon disrupts the continuous overlap of p orbitals. As a result, cycloheptatriene is not aromatic.
Removing one hydrogen from the intervening CH2 group...
Removing one hydrogen from the intervening CH2 group...
3.1K
02:11Conformations of Cyclohexane
13.6K
Cyclohexane does not exist in a planar form due to the high angle and torsional strain it would experience in the planar structure. Instead, it adopts non-planar chair and boat conformations.
The chair form is the most stable and derives its name from its resemblance to the “easy chair.” In the chair conformation, two carbon atoms are arranged out-of-plane — one above and one below, minimizing the torsional strain. In the chair form, the bond angle is very close to the ideal...
The chair form is the most stable and derives its name from its resemblance to the “easy chair.” In the chair conformation, two carbon atoms are arranged out-of-plane — one above and one below, minimizing the torsional strain. In the chair form, the bond angle is very close to the ideal...
13.6K
01:18Frost Circles for Different Conjugated Systems
3.0K
The inscribed polygon method is consistent with Hückel’s 4n + 2 rule and helps to learn whether the given cyclic compound is aromatic or not. The compound is stable and aromatic if every bonding molecular orbital (MO) is completely filled with a pair of electrons. However, if the non-bonding or antibonding orbitals are filled with electrons, the compound is unstable and not aromatic. Consider the Frost circle diagrams for cycloalkenes containing 4 to 8 carbons.
3.0K
01:18Aromatic Hydrocarbon Anions: Structural Overview
3.1K
Neutral hydrocarbons like cyclopentadiene with an odd number of carbon atoms and one intervening CH2 group in the ring are not aromatic. Cyclopentadiene with 4 π electrons does not satisfy the 4n + 2 π electron rule. Additionally, the intervening CH2 group is sp3 hybridized and lacks a vacant p orbital, thereby interrupting the overlap of p orbitals in a continuous manner and preventing the delocalization of π electrons throughout the ring.
Due to the absence of continuous...
Due to the absence of continuous...
3.1K