Carbazole-porphyrin-based COF: Synthesis, Characterization and Properties of Fluorescence and Iodine Adsorption

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 exhibited iodine vapor adsorption capacity of 2.37g g-1. XPS and Raman spectra suggested that both physisorption and chemisorption were present during iodine adsorption and the mechanism of the adsorption was studied by GCMC and DFT calculation. The electric conductivity of iodine-bearing Cz-TA-COF was investigated and it showed the conductivity increased by 6 orders of magnitude by iodine-doping. The emission bands of the COF exhibited excitation-wavelength-dependent and solvent-dependent properties. Cz-TA-COF gave dual emitting fluorescence in polar solvent and could be used as ratiometric temperature sensor.