Guest-Induced Structural Torsion in Single Covalent Organic Frameworks for Enhanced Photocatalysis
Yang Liu1,2, Hongbing Chi1, Yifei Tan1
1School of Nuclear Science & Technology, Southwest University of Science and Technology, Mianyang 621010, P. R. China.
Abstract:
Monitoring and understanding the photocatalytic reactions at individual covalent organic framework (COF) photocatalysts are crucial for gaining insights into their structure-activity relationships. Here, we report real-time imaging of the guest-induced structural torsion in single COF-300 microcrystals for enhanced photocatalysis utilizing in situ dark-field optical microscopy (DFM). Upon inclusion of ethyl acetate (EAC) into the COF-300 framework, deformed EAC-encapsulated COF-300 (EAC@COF-300) microcrystals with twisted diimine linkers are generated, resulting in an inert-to-active photocatalytic reactivity transformation. Impressively, this host-guest-enhanced photocatalysis strategy is also applicable to other guests. The combination of single-particle imaging, spectral characterizations, and theoretical calculations elucidates that structurally twisted EAC@COF-300 boosts the intersystem crossing process and spin-orbit coupling, facilitating the separation of photogenerated electron-hole pairs. Furthermore, the twisted EAC@COF-300 realizes the photocatalytic removal of radioactive 131I- at the pg level. Our findings provide a general strategy for the rational design of efficient COF photocatalysts via twist engineering.
Related Concept Videos
02:11Conformations of Cyclohexane
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...
01:26Photochemical Electrocyclic Reactions: Stereochemistry
Selection Rules: Photochemical Activation
02:46Crystal Field Theory - Tetrahedral and Square Planar 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,...
02:58Crystal Field Theory - Octahedral Complexes
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...
02:02Chair Conformation of Cyclohexane
The hydrogen atoms linked to carbons are arranged in two different axial and equatorial orientations to achieve this...
01:17Thermal Electrocyclic Reactions: Stereochemistry
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.