Enhancing the Iodine Adsorption Capacity of Pyrene‐Based Covalent Organic Frameworks by Regulating the Pore Environment

Abstract

Regulating of pore environment is an efficient way to improve the performance of covalent organic frameworks (COFs) for specific application requirements. Herein, the design and synthesis of two pyrene‐based 2D COFs with ‐H or ‐Me substituents, TFFPy‐PPD‐COF and TFFPy‐TMPD‐COF are reported. Both of them show long order structure and high porosity, in which TFFPy‐PPD‐COF displays a larger pore volume and bigger BET surface area (2587 m2 g−1, 1.17 cm3 g−1). Interestingly, TFPPy‐TMPD‐COF exhibits a much higher vapor iodine capacity (4.8 g g−1) than TFPPy‐PPD‐COF (2.9 g g−1), in contrast to their pore volume size. By using multiple techniques, the better performance of TFPPy‐TMPD‐COF in iodine capture is ascribed to the altered pore environment by introducing methyl groups, which contributes to the formation of polyiodide anions and enhances the interactions between the frameworks and iodine. These results will be helpful for understanding the effect of pore environment in COFs for iodine uptake and constructing novel structure with high iodine capture performance.

Construction of a conjugated covalent organic framework for iodine capture

“…S8 †). Although the surface area and pore volume of TPB-TMPD-COF was lower than that of reported TFPPy-TMPD-COF, 19 the comparable iodine adsorption capacity of TPB-TMPD-COF suggested increasing the density of adsorption sites was an efficient way to improve iodine adsorption capacity.…”

“…Due to their high surface area, low density and regular pore structure, COFs are suitable as a solid-phase adsorbent and have been studied as adsorbent materials for iodine capture. [10][11][12][13][14][15][16][17][18][19][20][21] For example, Fang et al synthesized tetrathiafulvalene-based COFs and achieved excellent iodine adsorption capacity through the synergistic effect of physical and chemical adsorption. 16 Recently we have also reported a pyrene-based two-dimensional COF (TFPPy-TMPD-COF) with a vapor capacity of 4.8 g g −1 due to the combination of chemisorption and physisorption, 19 in which the introduction of 2,3,5,6-tetramethyl-p-phenylenediamine (TMPD) was helpful for changing the pore environment to enhance the iodine adsorption capacity of the COF.…”

“…[10][11][12][13][14][15][16][17][18][19][20][21] For example, Fang et al synthesized tetrathiafulvalene-based COFs and achieved excellent iodine adsorption capacity through the synergistic effect of physical and chemical adsorption. 16 Recently we have also reported a pyrene-based two-dimensional COF (TFPPy-TMPD-COF) with a vapor capacity of 4.8 g g −1 due to the combination of chemisorption and physisorption, 19 in which the introduction of 2,3,5,6-tetramethyl-p-phenylenediamine (TMPD) was helpful for changing the pore environment to enhance the iodine adsorption capacity of the COF. However, the relatively low density of chemical adsorption sites (e.g., C]N group) in TFPPy-TMPD-COF still restricted its iodine capacity.…”