3D Ln-MOFs as multi-responsive luminescent probes for efficient sensing of Fe3+, Cr2O72−, and antibiotics in aqueous solution

Two families of lanthanide metal–organic frameworks (Ln-MOFs), namely {[Ln2L2(DMF)4]·xDMF·yH2O}n (Ln = Ce(1), Pr(2), Sm(3), Eu(4), Gd(5); x = 0, 1; y = 0, 1) and {[Ln2L2(H2O)2.5]}n (Ln = Dy(6), Ho(7)), have been solvothermally synthesized based on the semi-rigid tripodal ligand 5-(4-carboxybenzyloxy)isophthalic acid (H3L). Utilizing the excellent luminescence property and water stability, Eu(4) exhibited efficient luminescence responses toward Fe3+, Cr2O72−, and NFT/NZF antibiotics in aqueous medium with high sensitivity and selectivity. The detection limits (LODs) are 3.69 μM for Fe3+ ion, 4.01 μM for Cr2O72− anion and 9.92 μM/11.4 μM for NFT/NZF antibiotics, suggesting that Eu(4) is a good and simple multifunctional luminescent sensor. Additionally, the Gd(III) ions exhibit a weak antiferromagnetic interaction in the dinuclear SBUs of Gd(5), and Dy(6) shows slow magnetic relaxation behaviors under zero dc field.