Old Bottles of New Wines: Dynamic Multimode Color-Tuning Long Afterglow and White Light Emission in Cost-Effective Metal-Organic Frameworks (MOFs)

Abstract

Metal–organic frameworks (MOFs) with long afterglow luminescence (LAL) have gained attention for applications in light-emitting devices and anticounterfeiting. However, developing cost-effective and high-performance dynamic multicolor LAL MOFs remains challenging. Here, the rigid organic ligand 5-fluoronicotinic acid (FL), which incorporates a F atom to form molecular interlocking and inhibit nonradiative transitions, was chosen to self-assemble with MCl₂ (M = Zn and Cd) to fabricate long-lived phosphorescent MOFs. The synthesized MOFs, namely, FLCd, FLZn, and FLCd-DMF, exhibit excitation-dependent luminescence, ranging from blue/cyan to green, with cold white light emissions under specific excitations. Furthermore, all MOFs achieve dynamic color-tuning LAL based on excitation wavelength and temperature. Photoluminescence properties and theoretical calculations indicate that the multicolor LAL arises from the emissions of FL and its aggregation state, while enhanced phosphorescence can be assigned to heavy-atom and interlocking effects, coordination, and noncovalent interactions. Additionally, by leveraging their LAL behavior, these MOFs are applied for encrypting/decrypting information.