Interpenetration Transformation of Diacetylene Metal–Organic Frameworks for Topochemical Polymerization

ABSTRACT Achieving precise control over topochemical polymerization in diacetylene metal–organic frameworks (MOFs) remains a huge challenge due to the stringent requirements for molecular alignment and ordered stacking. Herein, we report two interpenetrated MOFs (twofold interpenetrated CAS‐20 and threefold interpenetrated CAS‐22) from a diacetylene ligand and Zn nitrate, and systematically unveil their interpenetration transformation proceeds through dramatic changes with a set of non‐interpenetrated semi‐crystalline intermediates (CAS‐20‐d, CAS‐21, CAS‐21‐d) accompanied by guest loss. This semi‐crystalline state is driven by non‐synchronous transformations of two individual frameworks in interpenetrated CAS‐20, jointly revealed through crystallographic analysis and detailed spectroscopic characterization. Remarkably, this interpenetration transformation promotes the diacetylene groups arranged in a suitable ordered and continuous stacking manner, enabling thermally induced topochemical polymerization in CAS‐22 via a 1,4‐addition reaction. The results confirm that the obtained interpenetrated MOFs show classic nonlinear optical limiting performance, and the polymerized CAS‐22 exhibits a remarkably enhanced third‐order nonlinear absorption coefficient compared to CAS‐20 (∼69 times). This study pioneers interpenetration transformation as a novel strategy for realizing MOF topochemical polymerization, opening new avenues for designing high‐performance optoelectronic materials for smart sensing and laser protection applications.