Beyond the Multicomponent Debus–Radziszewski Route: Two-Component Cyclocondensation Constructing a 12 + 3-Connected aea Topology Three-Dimensional Imidazole-Linked COF for Sustainable Wastewater Treatment

The rational construction of high-connectivity three-dimensional covalent organic frameworks (3D COFs) remains a central challenge in reticular chemistry, holding immense promise for advancing framework rigidity, porosity, and functional integration. From both fundamental and application standpoints, diversifying the linkage chemistry of such high-connectivity COFs beyond the archetypal imine bond is essential, as imidazole linkages impart superior chemical resilience, enhanced π-delocalization, and intrinsic polarity compared with imine linkages. Here, we report TU-123, the first 12 + 3-connected 3D imidazole-linked COF with aea topology, synthesized via a two-component cyclocondensation between a D₃-symmetric hexakis-aldehyde and a D_3h-symmetric hexaamine building block. Unlike conventional imidazole-linked COFs derived from multicomponent Debus-Radziszewski reactions, TU-123 forms through direct imidazole ring formation from aldehyde and amine precursors via an imine intermediate, intramolecular cyclization, and oxidative aromatization. This strategy, previously limited to 2D frameworks, is extended herein to a highly connected 3D network for the first time. Benefiting from its rigid and polarized imidazole framework, TU-123 exhibits a cationic surface character at neutral pH, arising from protonation of nitrogen sites within the imidazole linkages, which enables selective adsorption of anionic dyes such as acid orange 7, with a maximum adsorption capacity of 495.07 mg g^-1 and 86.08% removal efficiency under optimized conditions. The adsorption process follows pseudo-second-order kinetics and Langmuir isotherm behavior, highlighting the framework's potential for sustainable wastewater purification.