Atomic observation and structural evolution of covalent organic framework rotamers
Tengwu Zeng1, Yang Ling1,2, Wentao Jiang1
1School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China.
Summary
Dynamic covalent organic frameworks (COFs) exhibit adaptive gas adsorption. Researchers observed COF rotamers and structural evolution, enhancing methane uptake capacity by 100% through progressive structural transformation.
Area of Science:
- Materials Science
- Supramolecular Chemistry
- Crystallography
Background:
- Dynamic 3D covalent organic frameworks (COFs) display structural transformation and adaptive gas adsorption.
- Observing COF rotamers is challenging due to similar free energies and subtle rotational barriers.
Purpose of the Study:
- To achieve atomic-level observation and structural evolution of COF rotamers.
- To investigate the dynamic responses of COF-320 upon guest molecule inclusion.
Main Methods:
- Cryo-3D electron diffraction
- Synchrotron powder X-ray diffraction
- Optimization of COF-320 crystallinity and morphology
Main Results:
- Observed significant crystal expansion (29 vol% hydration, 78 vol% solvation).
- Recorded structural evolution from non-porous to expanded phases using n-butane.
- Uncovered biphenylene rotational freedom leading to conformational changes in diimine motifs (synclinal, syn-periplanar, anticlinal rotamers).
- Demonstrated a 10-fold increase in pore volumes and 100% enhancement in methane uptake capacity.
Conclusions:
- The study provides atomic-level insights into COF rotamer dynamics and structural evolution.
- Findings highlight the potential of progressive structural transformation in designing advanced porous materials for enhanced gas uptake.
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