Three-dimensional covalent organic frameworks with nia nets for efficient separation of benzene/cyclohexane mixtures

Abstract The synthesis of three-dimensional (3D) covalent organic frameworks (COFs) with highly connected building blocks presents a significant challenge. In this study, we report two novel 3D COFs with the nia topology, named JUC-641 and JUC-642, by introducing planar hexagonal and triangular prism nodes for the first time. The resulting materials display high crystallinity, excellent thermal/chemical stability, a through-hole structure, and a large specific surface area. Notably, our adsorption studies and breakthrough experiments reveal that both COFs exhibit exceptional separation capabilities, surpassing previously reported 3D COFs and most porous organic polymers, with a separation factor of up to 2.02 for benzene and cyclohexane. Additionally, dispersion-corrected density functional theory analysis suggests that the outstanding performance of these 3D COFs can be attributed to the incorporation of highly aromatic building blocks and the presence of extensive pore structures. Consequently, this research not only expands the diversity of COFs but also highlights the potential of functional COF materials as promising candidates for environmentally-friendly separation applications.