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Abstract Emissive covalent organic frameworks (COFs) have recently emerged as next‐generation porous materials with attractive properties such as tunable topology, porosity, and inherent photoluminescence. Among the different types of COFs, substoichiometric frameworks (so‐called Type III COFs) are especially attractive due to the possibility of not only generating unusual topology and complex pore architectures but also facilitating the introduction of well‐defined functional groups at precise locations for desired functions. Herein, the first example of a highly emissive (PLQY 6.8%) substoichiometric 2D‐COF (COF‐SMU‐1) featuring free uncondensed aldehyde groups is reported. In particular,COF‐SMU‐1features a dual‐pore architecture with an overallbexnet topology, tunable emission in various organic solvents, and distinct colorimetric changes in the presence of water. To gain further insights into its photoluminescence properties, the charge transfer, excimer emission, and excited state exciton dynamics ofCOF‐SMU‐1are investigated using femtosecond transient absorption spectroscopy in different organic solvents. Additionally, highly enhanced atmospheric water‐harvesting properties ofCOF‐SMU‐1are revealed using FT‐IR and water sorption studies.The findings will not only lead to in‐depth understanding of structure–property relationships in emissive COFs but also open new opportunities for designing COFs for potential applications in solid‐state lighting and water harvesting.
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Pyrene‐Based Polyimide Covalent Organic Framework with Temperature‐Dependent Fluorescence
Abstract The synthesis of a fluorescent covalent organic framework (COF) using perylene and pyrene building blocks (PEPy‐COF), via a one‐pot condensation reaction is reported. PEPy‐COF is crystallized into 2D nanosheets with a cubic and prismatic crystalline morphology and demonstrates structural stability at temperatures up to 500 °C. The structural morphology is confirmed using X‐ray diffraction and atomic‐level simulations. These 2D porous polymer sheets form a tetragonal framework that is found to have a high specific surface area of 772 m2g−1. Based on the definition of porous materials, the network is mesoporous with an observed pore size of 3.03 nm, which is in good agreement with the material's calculated pore size. The experimentally obtained HOMO‐LUMO band gap is 2.62 eV, confirming the semiconducting nature of PEPy‐COF. PEPy‐COF emits a shiny blue luminescence under UV and visible light. This luminescence intensity is temperature‐dependent in solvents with different polarities and dielectric constants demonstrating that the PEPy‐COF has potential use in a wide range of temperature‐sensing devices. The fluorescence intensity ratio is similar for different temperatures under ultra‐sound conditions and varying solvents.
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- Award ID(s):
- 1719875
- PAR ID:
- 10409510
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Optical Materials
- Volume:
- 11
- Issue:
- 14
- ISSN:
- 2195-1071
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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