Robust Co(II)-Based Metal–Organic Framework for the Efficient Uptake and Selective Detection of SO2

MUF-16 is a porous metal–organic framework comprising cobalt(II) ions and 5-aminoisophthalate ligands. Here, we measured its reversible SO2 adsorption–desorption isotherm around room temperature and up to 1 bar and observed a high capacity for SO2 (2.2 mmol g–1 at 298 K and 1 bar). The uptake of SO2 was characterized by Fourier transform infrared (FT-IR) spectroscopy, which indicated hydrogen bonding between the SO2 guest molecules and amino functional groups of the framework. The location and packing of the SO2 molecules were confirmed by computational studies, namely, density functional theory (DFT) calculations of the strongest adsorption site and grand canonical Monte Carlo (GCMC) simulations of the adsorption isotherm. Furthermore, MUF-16 showed a remarkable selective fluorescence response to SO2 compared to other gases (CO2, NO2, N2, O2, CH4, and water vapor). The possible fluorescence mechanism was determined by using time-resolved photoluminescence. Also, the limit of detection (LOD) was calculated to be 1.26 mM (∼80.72 ppm) in a tetrahydrofuran (THF) solution of SO2.