A copper(<sc>ii</sc>)-based metal-organic framework: electrochemical sensing of Cd(<sc>ii</sc>) and Pb(<sc>ii</sc>) and adsorption of organic dyes

A new inorganic-organic hybrid complex, namely [Cu3L2(DMF)2]<middle dot>H2O (Cu-L), has been synthesized using a sulfur-rich ligand, 3,3 ',3 ''-(1,3,5-triazine-2,4,6-triyltrisulfanediyl)tripropanoic acid (H3L) and metal cations under hydrothermal conditions. The metal atoms are interconnected to form a paddle-wheel-like structure, which is ultimately linked to the ligands to create a three-dimensional architecture. Cu-L, employed to fabricate an electrochemical sensor denoted as Cu-L@GCE (glassy carbon electrode), is capable of simultaneously detecting Cd2+ and Pb2+ at approximately -0.82 V and -0.58 V (vs. Ag/AgCl reference), exhibiting high sensitivity and selectivity. Cu-L@GCE demonstrates broad linear detection ranges of 8-28 mu M for Cd2+ and 2-14 mu M for Pb2+, along with low limit of detection (LOD) values of 0.01363 mu M and 0.00212 mu M, respectively. Furthermore, Cu-L@GCE achieves LOD values of 0.00209 mu M and 0.000034 mu M when detecting both ions simultaneously. The constructed sensor successfully detects Cd2+ and Pb2+ in mineral water, tap water, and river water with satisfactory recoveries. Additionally, the adsorption performance for organic dyes has been studied in detail using Cu-L as an adsorbent. The results indicate good adsorption selectivity for methylene blue (MB) and neutral red (NR) compared to methyl orange (MO) and rhodamine B (RhB) molecules.