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. 2022 Apr 6;13(1):1882.
doi: 10.1038/s41467-022-29565-1.

Multiple yet switchable hydrogen-bonded organic frameworks with white-light emission

Yadong Shi  1 , Shuodong Wang  2 , Wei Tao  1 , Jingjing Guo  3 , Sheng Xie  2 , Yanglan Ding  1 , Guoyong Xu  1 , Cheng Chen  1 , Xiaoyu Sun  4 , Zengming Zhang  4 , Zikai He  5 , Peifa Wei  6   7 , Ben Zhong Tang  8
Affiliations

Multiple yet switchable hydrogen-bonded organic frameworks with white-light emission

Yadong Shi et al. Nat Commun. .

Abstract

The development of new strategies to construct on-demand porous lattice frameworks from simple motifs is desirable. However, mitigating complexity while combing multiplicity and reversibility in the porous architectures is a challenging task. Herein, based on the synergy of dynamic intermolecular interactions and flexible molecular conformation of a simple cyano-modified tetraphenylethylene tecton, eleven kinetic-stable hydrogen-bonded organic frameworks (HOFs) with various shapes and two thermo-stable non-porous structures with rare perpendicular conformation are obtained. Multimode reversible structural transformations along with visible fluorescence output between porous and non-porous or between different porous forms is realized under different external stimuli. Furthermore, the collaborative of flexible framework and soft long-chain guests facilitate the relaxation from intrinsic blue emission to yellow emission in the excited state, which represents a strategy for generating white-light emission. The dynamic intermolecular interactions, facilitated by flexible molecular conformation and soft guests, diversifies the strategies of construction of versatile smart molecular frameworks.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Fig. 1
Fig. 1. Tunable emission based on dynamic intermolecular interactions in switchable HOFs.
The purple and yellow dashed lines indicate hydrogen bonding and π–π interactions, respectively. ‘θ’ indicates the dihedral angles between four phenyl groups and the central ethenyl group.
Fig. 2
Fig. 2. Investigation of single-crystal structures of 4CN(Non1).
a UV-Vis diffuse reflectance spectra (left) and PL spectra (right) of 4CN(Non1) crystals. λex = 365 nm. Inset: the photograph of 4CN(Non1) crystals under daylight (left) and UV light (right). b The PXRD patterns of simulated 4CN(Non1) crystals, ground 4CN(Non1) crystals, fumed 4CN(Non1) crystals with different solvents. c ESP diagram of 4CN. d The dihedral angles between four phenyl groups and central ethenyl group of 4CN(Non1) crystals. e Crystal packing of 4CN(Non1) with labeled π–π stacking interactions.
Fig. 3
Fig. 3. Multiple emissive crystals of 4CN.
a The photographs of different crystals of 4CN under daylight (first row) and UV light (second row). b Normalized fluorescent emission spectra of different crystals. c The corresponding simulated PXRD patterns of different crystals, that is, 4CN(ET2) and 4CN(MT) in group 1 (G1), 4CN(ET1) in group 2 (G2), 4CN(Non1) and 4CN(Non2) in group 3 (G3) or 4CN(THF), 4CN(DCM) and 4CN(TCM) in group 4 (G4).
Fig. 4
Fig. 4. Multiple white-light emissive crystals of 4CN.
a Packing diagram of 4CN(Hex) along the [001] direction and [100] direction. The dimensions of the cavity are highlighted by red arrows. b Normalized fluorescent emission spectra of 4CN(Hex), 4CN(Hep), 4CN(Oct), 4CN(Dec) and 4CN(Dod) crystals. Inset: fluorescent images of 1 for 4CN(Hex), 2 for 4CN(Hep), 3 for 4CN(Oct), 4 for 4CN(Dec) and 5 for 4CN(Dod) crystals. c The corresponding CIE chromaticity coordinates in CIE-1931 chromaticity diagram for 1–5. d PL spectra of 4CN(Hex) after grinding. Inset: the PXRD patterns of simulated 4CN(Hex) and its ground sample. e Time-resolved emission spectra of 4CN(Hex) crystal. λex = 343 nm. f Proposed mechanism for white light emitting crystals.
Fig. 5
Fig. 5. The transformation of 4CN(Hex).
a TGA, b DSC, and c variable-temperature PXRD of 4CN(Hex) crystals upon heating. d Structure transformation between porous 4CN(Hex) or 4CN(ET2) and nonporous 4CN(Non1) upon heating and solvent fuming. ‘Δ’ indicates heating.
Fig. 6
Fig. 6. Multimode reversible transformations of 4CN.
a Packing diagram of G1: 4CN(ET2) and 4CN(MT). b Packing diagram of G2: 4CN(ET1), 4CN(Hex), 4CN(Hep), 4CN(Oct), 4CN(Dec), and 4CN(Dod). c Packing diagram of G4: 4CN(THF), 4CN(DCM), and 4CN(TCM). d Packing diagram of G3: 4CN(Non1) and 4CN(Non2). ‘Δ’ indicates heating.
See this image and copyright information in PMC

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