| 1. |
- Gao, Chao, et al.
(författare)
-
Isostructural Three-Dimensional Covalent Organic Frameworks
- 2019
-
Ingår i: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 58:29, s. 9770-9775
-
Tidskriftsartikel (refereegranskat)abstract
- Herein, we reported the designed synthesis of three isostructural three-dimensional covalent organic frameworks (3D COFs) with -H, -Me, or -F substituents, which have similar crystallinity and topology. Their crystal structures were determined by continuous rotation electron diffraction (cRED), and all three 3D COFs were found to adopt a fivefold interpenetrated pts topology. More importantly, the resolution of these cRED datasets reached up to 0.9-1.0 angstrom, enabling the localization of all non-hydrogen atomic positions in a COF framework directly by 3D ED techniques for the first time. In addition, the precise control of the pore environments through the use of different functional groups led to different selectivities for CO2 over N-2. We have thus confirmed that polycrystalline COFs can be definitely studied to the atomic level as other materials, and this study should also inspire the design and synthesis of 3D COFs with tailored pore environments for interesting applications.
|
|
| 2. |
- Li, Jian, et al.
(författare)
-
Atomic-resolution structures from polycrystalline covalent organic frameworks with enhanced cryo-cRED
- 2022
-
Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 13:1
-
Tidskriftsartikel (refereegranskat)abstract
- The pursuit of atomic precision structure of porous covalent organic frameworks (COFs) is the key to understanding the relationship between structures and properties, and further developing new materials with superior performance. Yet, a challenge of how to determine their atomic structures has always existed since the first COFs reported seventeen years ago. Here, we present a universal method for ab initio structure determination of polycrystalline three-dimensional (3D) COFs at atomic level using enhanced cryo-continuous rotation electron diffraction (cryo-cRED), which combines hierarchical cluster analysis with cryo-EM technique. The high-quality datasets possess not only up to 0.79-angstrom resolution but more than 90% completeness, leading to unambiguous solution and precise refinement with anisotropic temperature factors. With such a powerful method, the dynamic structures with flexible linkers, degree of interpenetration, position of functional groups, and arrangement of ordered guest molecules are successfully revealed with atomic precision in five 3D COFs, which are almost impossible to be obtained without atomic resolution structure solution. This study demonstrates a practicable strategy for determining the structures of polycrystalline COFs and other beam-sensitive materials and to help in the future discovery of novel materials on the other.
|
|
| 3. |
- Liang, Lin, et al.
(författare)
-
Non-Interpenetrated Single-Crystal Covalent Organic Frameworks
- 2020
-
Ingår i: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 59:41, s. 17991-17995
-
Tidskriftsartikel (refereegranskat)abstract
- Growth of covalent organic frameworks (COFs) as single crystals is extremely challenging. Inaccessibility of open-structured single-crystal COFs prevents the exploration of structure-oriented applications. Herein we report for the first time a non-interpenetrated single-crystal COF, LZU-306, which possesses the open structure constructed exclusively via covalent assembly. With a high void volume of 80 %, LZU-306 was applied to investigate the intrinsic dynamics of reticulated tetraphenylethylene (TPE) as the individual aggregation-induced-emission moiety. Solid-state(2)H NMR investigation has determined that the rotation of benzene rings in TPE, being the freest among the reported cases, is as fast as 1.0x10(4) Hz at 203 K to 1.5x10(7) Hz at 293 K. This research not only explores a new paradigm for single-crystal growth of open frameworks, but also provides a unique matrix-isolation platform to reticulate functional moieties into a well-defined and isolated state.
|
|
| 4. |
- Ma, Tianqiong, et al.
(författare)
-
Observation of Interpenetration Isomerism in Covalent Organic Frameworks
- 2018
-
Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 140:22, s. 6763-6766
-
Tidskriftsartikel (refereegranskat)abstract
- We report herein the first example of interpenetration isomerism in covalent organic frameworks (COFs). As a well-known three-dimensional (3D) COF, COF-300 was synthesized and characterized by the Yaghi group in 2009 as a 5-fold interpenetrated diamond structure (dia-cS topology). We found that adding an aging process prior to the reported synthetic procedure afforded the formation of an interpenetration isomer, dia-c7 COF-300. The 7-fold interpenetrated diamond structure of this new isomer was identified by powder Xray diffraction and rotation electron diffraction analyses. Furthermore, we proposed a universal formula to accurately determine the number of interpenetration degrees of dia-based COFs from only the unit cell parameters and the length of the organic linker. This work not only provides a novel example to the category of interpenetration isomerism but also provides new insights for the further development of 3D COFs.
|
|
| 5. |
- Xu, Hai-Sen, et al.
(författare)
-
Single crystal of a one-dimensional metallo-covalent organic framework
- 2020
-
Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 11:1
-
Tidskriftsartikel (refereegranskat)abstract
- Although polymers have been studied for well over a century, there are few examples of covalently linked polymer crystals synthesised directly from solution. One-dimensional (1D) covalent polymers that are packed into a framework structure can be viewed as a 1D covalent organic framework (COF), but making a single crystal of this has been elusive. Herein, by combining labile metal coordination and dynamic covalent chemistry, we discover a strategy to synthesise single-crystal metallo-COFs under solvothermal conditions. The single-crystal structure is rigorously solved using single-crystal electron diffraction technique. The non-centrosymmetric metallo-COF allows second harmonic generation. Due to the presence of syntactic pendant amine groups along the polymer chains, the metallopolymer crystal can be further cross-linked into a crystalline woven network. Although polymers have been studied for well over a century, there are few examples of covalently linked polymer crystals synthesized directly from solution. Here, the authors demonstrate a strategy to synthesize single crystalline 1D metallo-covalent organic frameworks by combining dynamic covalent chemistry and metal-ligand coordination.
|
|
