Structural Diversity and Highly Thermosensitivity of Diacetylene Lanthanide–Organic Frameworks

ABSTRACT

Topochemical polymerization enables additive‐free synthesis of precision polymers from preorganized monomers, yet achieving controlled geometric preorganization in metal–organic frameworks (MOFs) remains a formidable challenge. Here, we report the first systematic exploitation of Ln‐MOFs with lanthanide contraction effect to achieve topochemical polymerization for high thermochromic fluorescence. A family of Ln‐MOFs assembled from a rigid diacetylene ligand exhibits distinct polymerization behaviors depending on the framework architecture. Comprehensive structural investigations reveal that lanthanide contraction systematically dictates the phase distribution across the lanthanide series, while the specific polymerization pathway—phase‐transition‐assisted or direct—is determined by the inherent geometry of each framework. The successful polymerization is further corroborated by enhanced third‐order nonlinear optical responses, consistent with the formation of extended π‐conjugation. Notably, Eu‐MOF and Tb‐MOF exhibit distinct temperature‐dependent luminescence quenching behaviors, giving rise to pronounced asymmetric thermal sensitivity and showing potential for self‐calibrated ratiometric thermometry. This work demonstrates how lanthanide contraction directs structural diversity and how geometric preorganization governs topochemical polymerization in crystalline materials, opening new avenues for multifunctional smart materials.