Dimensionality‐Dependent Pressure‐Induced Emission Memory in Covalent Organic Frameworks

Stimuli‐responsive luminescent materials with memory effects hold significant promise for advanced applications in optical data storage and pressure sensing. We present the first crystalline covalent organic frameworks (COFs) exhibiting a pressure‐induced emission memory effect, characterized by persistent pressure‐induced emission enhancement (PIEE) that remains after decompression. Through the synthesis of a dimensional series of tetraphenylethylene‐based COFs—JUC‐730 and JUC‐731 (one‐dimensional, 1D), JUC‐732 (two‐dimensional, 2D), and JUC‐733 (three‐dimensional, 3D)—we systematically investigated how framework dimensionality governs photophysical responses under hydrostatic pressure. Remarkably, the 1D COFs exhibit pronounced PIEE, with JUC‐730 retaining a 2.4‐fold fluorescence enhancement post‐decompression, representing the first observation of an emission memory effect in COFs. In situ FT‐IR, powder X‐ray diffraction (PXRD), and DFT analyses demonstrate that this memory effect originates from anisotropic unit‐cell contraction, facilitated by conformational locking of flexible aryl–O–aryl (C–O–C) linkages in JUC‐730, which results in a binding energy of ∼4.79 eV that stabilizes the emissive state. By contrast, the 2D and 3D COFs either undergo fluorescence quenching or fail to retain emission enhancement due to irreversible structural changes. These results establish a clear structure–dimensionality–function relationship and provide a design strategy for mechanically programmable luminescent materials with tailored pressure‐responsive properties.