Design of turn-on fluorescence sensor for L-Cysteine based on the instability of metal-organic frameworks

Generally, instable metal-organic frameworks (MOFs) were seldom used in many applications compared to stable MOFs. However, due to the huge amount of these MOFs and the diversity of the instability, effective use of instable MOFs is necessary and important. As one of classical MOFs, Cu-BTC was applied in many fields including adsorption, separation and catalysis based on its stability. Different from the previous reports, this work mainly focuses on the special instability of Cu-BTC towards the thiol molecules. In detail, a fluorescent molecule (rhodamine B, RhB) was incorporated into Cu-BTC crystals through in-situ synthesis strategy to construct the new sensor, FthB@Cu-BTC. As expected, based on the collapse of Cu-BTC framework caused by L-Cysteine (L-Cys), RhB@Cu-BTC can sense this thiol-containing amino acid selectively and sensitively with naked eyes. The sensor also exhibits a low detection limit of 0.702 mu mol L-1.