Fluorescent Three‐Dimensional Covalent Organic Frameworks with pcu Topology Based on Triangular Antiprism Node

Abstract The design of highly connected fluorescent polyhedral building blocks is essential for expanding the structural and functional diversity of three‐dimensional covalent organic frameworks (3D COFs) but remains largely underexplored due to synthetic and characterization challenges. Here, we report a hexatopic fluorescent building block with triangular antiprismatic geometry, developed via steric‐hindrance‐directed conformational control and the integration of triphenylamine units. Its imine condensation with linear diamines afforded two crystalline 3D COFs with unambiguously resolved 6‐fold Class IIa interpenetrated pcu topology, as determined by continuous rotation electron diffraction. Interestingly, both COFs exhibit yellow‐green solid‐state fluorescence and high‐contrast piezofluorochromism under hydrostatic conditions. This work introduces a new class of fluorescent polyhedral nodes to expand the structural diversity of fluorescent 3D COFs and highlights their potential as stimuli‐responsive materials for interesting applications.