Controlling the Nucleation Process to Prepare a Family of Crystalline Tribenzimidazole-Based Covalent Organic Frameworks

Covalent organic frameworks (COFs) are at the forefront of porous material research due to their crystallinity and topological diversity. However, most COFs are connected by reversible chemical bonds, which limit their applications under harsh conditions. Herein, we develop a novel synthetic method to lock the imine bond using amino groups via a precursor-involved cascade reaction. We experimentally demonstrated that the nucleation process of COFs can be controlled by precursor hydrolysis. A family of crystalline two-dimensional tribenzimidazole-based COFs (2D BI-COFs) was prepared by the condensation of o-phenylenediamine derivative and aryl aldehydes. Their structures were confirmed by powder X-ray diffraction, Fourier-transform infrared spectroscopy, and solid-state 13C cross-polarization magic angle spinning nuclear magnetic resonance (CP/MAS NMR) spectroscopy. They showed high surface areas, good CO2 uptake capacities, excellent CO2/N2 selectivities, and high chemical stabilities. Of these materials, BI-COF-1 was an efficient photocatalyst for the visible-light-driven photocatalytic oxidation of sulfides, which displayed high conversion (∼100%) and excellent selectivity (>90%). We believe that our study can provide new insights into the synthesis of 2D chemical-stable COFs.