Moderate and Universal Synthesis of Undoped Covalent Organic Framework Aerogels for Enhanced Iodine Uptake

Abstract

The fabrication of hierarchically porous covalent organic framework (COF) aerogels is always challenging but of great significance in chemistry and materials science. The known COF aerogel preparation system is very limited and usually results in aerogel composite with low crystallinity. Herein, a universal and moderate synthetic strategy is presented for undoped COF aerogels through the catalysis of scandium trifluoromethanesulfonate. Due to the high catalytic activity of the scandium catalyst on aldimine condensation, densely distributed COF small crystal nuclei can be induced to be generated instantaneously under mild conditions, which leads to the immediate formation of crystalline COF gel within 5 min, whereas the traditional reaction system catalyzed by acetic acid is to form COF powder by slow accumulation of large two-dimensional lamellae. Thus, the COF morphology control based on the nucleation rate is realized. The hierarchically interconnected porous networks endow the obtained COF aerogels with enhanced adsorption performance for iodine, and the adsorption capacity can reach 8.15 g/g, which is among one of the highest iodine-sorbing values. This study provides a moderate and general method for the direct synthesis of undoped COF aerogels and has important significance for the processing and shaping of COF materials with prospective applications in efficient iodine uptake.

Chemically Stable and Heteroatom Containing Porous Organic Polymers for Efficient Iodine Vapor Capture and its Storage

“…37,70−72 On the other hand, the signal between ∼168 and 170 cm −1 in I 2 @HPOPs is assigned to the stretching vibration of I 5 − . 62,68,73 In general, the absence of peaks above 180 cm −1 in these Raman spectra clearly ruled out the presence of molecular iodine (I 2 ). Overall, the Raman spectra suggested that presence of elemental iodine in I 2 @HPOPs as polyiodide species.…”

“…The Raman spectra of I 2 @HPOPs show three distinct bands that are absent in the as-synthesized sample (Figure S11) of the corresponding HPOPs. The signal between ∼106 and 146 cm –1 in I 2 @HPOPs are assigned to symmetric and asymmetric stretching vibrations in I 3 – species. ,− On the other hand, the signal between ∼168 and 170 cm –1 in I 2 @HPOPs is assigned to the stretching vibration of I 5 – . ,, In general, the absence of peaks above 180 cm –1 in these Raman spectra clearly ruled out the presence of molecular iodine (I 2 ). Overall, the Raman spectra suggested that presence of elemental iodine in I 2 @HPOPs as polyiodide species.…”

Green mechanochemical synthesis of imine-linked covalent organic frameworks for high iodine capture

“…S25†), which is similar to previous reports. 19,25,55,56 FTIR analysis verified the chemical integrity of the used MC-DMTP–TPB COF (Fig. S26†).…”

Facile Microwave-Assisted Synthesis of 2D Imine-Linked Covalent Organic Frameworks for Exceptional Iodine Capture

“… FT-IR profile implied the charge transfer between imine N and iodine molecules, which was further corroborated by XPS analysis. As depicted in Figure A, the I 3d XPS spectra of I 2 @Mw-TFB-BD-CH 3 displayed I 3d 3/2 signals at 630.1 and 631.8 eV as well as I 3d 5/2 signals at 618.5 and 620.1 eV, which were ascribed to the formation of triiodide (I 3 – ) and pentaiodide (I 5 – ) anions. ,− Based on the integral area of XPS peaks, I 3 – and I 5 – species occupy 46% and 54% of the total I 2 uptake for I 2 @Mw-TFB-BD-CH 3 . In contrast, I 3 – and I 5 – species take up 60% and 40% of the total I 2 uptake for I 2 @Mw-TFB-BD-OCH 3 (Figure B), indicating the pore surface environment affected the polyiodide formation.…”