Strontium-Based MOFs Showing Dual Emission: Luminescence Thermometers and Toluene Sensors
Pedro Leo, David Briones, José A. Fuentes, Javier Cepeda, Gisela Orcajo, Guillermo Calleja, Antonio Rodríguez‐Diéguez, Fernando Martı́nez
Abstract
This work reports on the preparation and optical characterization of two metal–organic frameworks (MOFs) based on strontium ions and 2-amino-1,4-benzenedicarboxylate (NH2-bdc) ligand: i.e., [Sr(NH2-bdc)(DMF)]n (1) and {[Sr(NH2-bdc)(Form)]·H2O}n (2) (where DMF = dimethylformamide and Form = formamide). Compound 1 has a 3D architecture built up from the linkage established by NH2-bdc among metal–carboxylate rods, leaving significant microchannels that are largely occupied by DMF molecules coordinated to strontium centers. The solvent molecules play a crucial role in the photoluminescence (PL) properties, which has been deeply characterized by diffuse reflectance and variable-temperature emission. Interestingly, both materials present intriguing photoluminescence (PL) properties involving intense short-lived and long-lasting phosphorescence (LLP), though the latter is especially remarkable for compound 2 with a lifetime of 815 ms at low temperature. Conversely, the strong PL shown by 1 may be successfully exploited due to both its luminescent thermochromism observed in the RT to 10 K range and its solvent-dependent PL sensing capacity, imbuing this material with potential activity as a PL thermometer as well as a toluene detector in water solutions.