Ordered Macro–Microporous Single Crystals of Covalent Organic Frameworks with Efficient Sorption of Iodine

Abstract

Fashioning microporous covalent organic frameworks (COFs) into single crystals with ordered macropores allows for an effective reduction of the mass transfer resistance and the maximum preservation of their intrinsic properties but remains unexplored. Here, we report the first synthesis of three-dimensional (3D) ordered macroporous single crystals of the imine-linked 3D microporous COFs (COF-300 and COF-303) via a template-assisted modulated strategy. In this strategy, COFs crystallized within the sacrificial colloidal crystal template, assembled from monodisperse polystyrene microspheres, and underwent an aniline-modulated amorphous-to-crystalline transformation to form large single crystals with 3D interconnected macropores. The effects of the introduced macroporous structure on the sorption performances of COF-300 single crystals were further probed by iodine. Our results indicate that iodine adsorption occurred in micropores of COF-300 but not in the introduced macropores. Accordingly, the iodine adsorption capacity of COF single crystals was governed by their micropore accessibility. The relatively long diffusion path in the non-macroporous COF-300 single crystals resulted in a limited micropore accessibility (48.4%) and thus a low capacity in iodine adsorption (1.48 g•g −1 ). The introduction of 3D ordered macropores can greatly shorten the microporous diffusion path in COF-300 single crystals and thus render all their micropores fully accessible in iodine adsorption with a capacity (3.15 g•g −1 ) that coincides well with the theoretical one.

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

“…74 In particular, I 2 @ HPOPs well retained their structures that resembled "syrup filled rolls," which indicated that molecular iodine (I 2 ) did not condense in the pores of HPOPs. 69 As expected, the EDS analysis of each I 2 @HPOP (Figure S14a−d, Supporting Information) indicated a high iodine content due to the presence of iodine species in the pores and on the surface of HPOPs. 62,67 Finally, the TGAs (N 2 atmosphere) of I 2 @HPOPs samples were recorded, and the respective thermograms are shown in Figure S15 (Supporting Information).…”

“…62 Simultaneously, the PXRD data provided indirect evidence of the presence of amorphous polyiodide species in the pores and on the surface of HPOPs. 69 Next, insight into the morphological changes of I 2 @HPOPs were obtained from the corresponding FE-SEM images (Figure 5i and Figure S13, Supporting Information). The morphologies of I 2 @HPOPs were essentially unaffected following iodine adsorption when their SEM images were compared with that of the corresponding as-synthesized HPOPs.…”

An iodide-containing covalent organic framework for enhanced radiotherapy

“…S1I, ESI † ). 72 Thermogravimetric analysis showed that TDI-COF is thermally stable up to approximately 280 °C, demonstrating the absence of I 2 species in the pores (Fig. S1J, ESI † ).…”

Recent advances on covalent organic frameworks (COFs) as photocatalysts: different strategies for enhancing hydrogen generation

“…The discovery of single-crystal COFs is in the preliminary stages and a few synthetic methods have been discussed. [146][147][148][149][150][151][152] (2) Compared with the results achieved by 2D COFs in photocatalytic hydrogen precipitation, 3D COFs have been poorly explored. (3) Photocatalytic total hydrolysis for simultaneous hydrogen and oxygen evolution remains in its infancy.…”