Carborane-Based\nThree-Dimensional Covalent Organic\nFrameworks

Abstract

The predesignable porous structure\nand high structural flexibility\nof covalent organic frameworks (COFs) render this material desirable\nas a platform for addressing various cutting-edge issues. Precise\ncontrol over their composition, topological structure, porosity, and\nstability to realize tailor-made functionality still remains a great\nchallenge. In this work, we developed a new kind of three-dimensional\n(3D) carborane-based COF with a 7-fold interpenetrating <b>dia</b> topological diagram. The resulting COFs exhibited high crystallinity,\nexceptional porosity, and strong robustness. The slightly lower electronegativity\nof boron (2.04) than that of hydrogen (2.20) can lead to the polarization\nof the B–H bond into a B^δ+–H^δ− mode, which renders these COFs as high-performance materials for\nthe adsorption and separation of hexane isomers through the B–H^δ−···H^δ+–C\ninteraction. Significantly, the carborane content of obtained COFs\nreached up to 54.2 wt %, which gets the highest rank among all the\nreported porous materials. Combining high surface area, strong robustness,\nand high content of carborane, the obtained COFs can work as efficient\nadsorbents for the separation of the five hexane isomers with high\nseparation factors. This work not only enhances the diversity of 3D\nfunctional COFs but also constitutes a further step toward the efficient\nseparation of alkane isomers.