CYCU-3: an Al(III)-based MOF for SO₂ capture and detection

The Al(III)-based MOF CYCU-3 exhibits a relevant SO₂ adsorption performance with a total uptake of 11.03 mmol g^-1 at 1 bar and 298 K. CYCU-3 displays high chemical stability towards dry and wet SO₂ exposure. DRIFTS experiments and computational calculations demonstrated that hydrogen bonding between SO₂ molecules and bridging Al(III)-OH groups are the preferential adsorption sites. In addition, photoluminescence experiments demonstrated the relevance of CYCU-3 for application in SO₂ detection with good selectivity for SO₂ over CO₂ and H₂O. The change in fluorescence performance demonstrates a clear turn-on effect after SO₂ interaction. Finally, the suppression of ligand-metal energy transfer along with the enhancement of ligand-centered π* → π electronic transition was proposed as a plausible fluorescence mechanism.