Dynamic Upconversion Luminescence via Lattice Strain Engineering in Lanthanide‐Based Metal–Organic Frameworks

Abstract Upconversion (UC) luminescence has emerged as a promising candidate for cutting‐edge photonic applications spanning biological imaging, multi‐level security systems, and advanced anti‐counterfeiting. Nevertheless, the intrinsic rigidity of conventional crystalline matrices imposes critical limitations on their dynamically responsive modulation capabilities, particularly constraining progress in confidential information protection. Herein, an innovative lattice strain engineering strategy is proposed that enables stimuli‐responsive UC characteristics in lanthanide‐incorporated metal–organic frameworks (Ln‐MOFs) through intentionally distorting their topological network. The engineered lattice strain effectively boosts the sensitizer‐to‐activator energy transfer and concurrently suppresses vibration‐induced non‐radiative decay, thereby activating the UC emission channels. Crucially, a thermally responsive UC modulation is achieved through regulating the lattice strain based on a negative thermal expansion mechanism, demonstrating substantial potential for advanced information security applications. These findings open new avenues for precise engineering of MOF architectures via localized chemical modifications toward the function‐oriented construction of responsive MOF‐based UC materials.