A carbazole–porphyrin-based COF: synthesis, characterization, and fluorescence and iodine adsorption properties

Abstract

Due to their ordered pore structure, large surface area and tunable functionality, covalent organic frameworks (COFs) offer potential for applications as sensors and adsorbents. In this study, we report the design and synthesis of a new carbazole–porphyrin-based COF (Cz-TA-COF) with a two-dimensional structure featuring eclipsed AA stacking, which was characterized using XRD, solid-state ¹³C NMR, IR, TGA, BET, DRS and CV. Cz-TA-COF exhibits high crystallinity, good stability, and extensive absorption of visible light. Cz-TA-COF shows a high BET specific surface area up to 576 m² g⁻¹ and an iodine vapor adsorption capacity of 2.37 g g⁻¹. XPS and Raman spectra suggested that both physisorption and chemisorption occur during iodine adsorption and the mechanism of the adsorption was studied by GCMC and DFT calculations. The electrical conductivity of iodine-bearing Cz-TA-COF was investigated and it showed an increase in conductivity by 6 orders of magnitude due to iodine-doping. The emission bands of the COF exhibited excitation-wavelength-dependent and solvent-dependent properties. Cz-TA-COF exhibited dual emitting fluorescence in polar solvents and could be used as a ratiometric temperature sensor.