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A new ABW-type luminescent metal–organic framework (MOF) namely (H3O)[Zn2L(H2O)]·3NMP·6H2O (1), constructed with eco-friendly Zn2+ and the multicarboxylate intraligand (LH5) was designed, synthesized and fully characterized by X-ray single-crystal diffraction, steady-state absorption and emission spectroscopy, and SEM observations. The MOF-based suspension sensor 1 (NMP) demonstrated high sensitivity to low-concentration pesticides of chlorothalonil (CTL), nitrofen (NF), trifluralin (TFL), and 2,6-dichloro-4-nitroaniline (DCN), which was assigned to the synergistic effect of the photoinduced electron transfer and the fluorescence resonance energy transfer. With the highest luminescent detection efficiency (KSV up to 11.194 μmol−1 and LOD down to 2.93 ppm) to DCN, 1 (NMP) was successfully applied for the selective sensing of DCN. The MOF-based film sensor 1 (film) illustrated the selective visualization sensing of trace amounts of DCN. In addition, based on the high saturated vapor pressure of TFL and the unique bathochromic shift effect to the emission maxima of 1, the MOF-based luminescent vapor sensing device 1 (LED) successfully exhibited operability for sensing of TFL vapor. The results illustrated a feasible approach to construct new MOF-based luminescent sensors for selective sensing and visualization of pesticides.

A series of binuclear dysprosium compounds, namely, [Dy(api)]2 (1), [Dy(api)]2·2CH2Cl2 (2), [Dy(Clapi)]2·2C4H8O (3), and [Dy(Clapi)]2·2C3H6O (4) (H3api = 2-(2-hydroxyphenyl)-1,3-bis[4-(2-hydroxyphenyl)-3-azabut-3-enyl]-1,3-imidazoline; H3Clapi = 2-(2′-hydroxy-5′-chlorophenyl)-1,3-bis[3′-aza-4′-(2′′-hydroxy-5′′-chlorophenyl)prop-4′-en-1′-yl]-1,3-imidazolidine), have been isolated by the reactions of salen-type ligands H3api/H3Clapi with DyCl3·6H2O in different solvent systems. Structural analysis reveals that each salen-type ligand provides a heptadentate coordination pocket (N4O3) to encapsulate a DyIII ion and all of the DyIII centers in 1–4 adopt a distorted square antiprism geometry with D4d symmetry. Magnetic studies showed that compound 1 did not exhibit single-molecule magnetic (SMMs) behavior. With the introduction of different lattice solvents, compounds 2–4 showed filed-induced slow magnetic relaxation with barriers Ueff of 18.2 K (2), 28.0 K (3) and 16.4 K (4), respectively. Ab initio calculations were employed to interpret the magnetization behavior of 1–4. The combination of experimental and theoretical data reveal the importance of the weak exchange interaction between the DyIII ions in the observation of slow magnetic relaxation, and a relaxation mechanism has been developed to rationalize the observed difference in the Ueff values. The different lattice solvents influence Dy–O–Dy bond angles and thus alter the torsion of the square antiprism geometry, consequently resulting in distinct magnetic interactions and the magnetic behavior.

A series of binuclear dysprosium compounds, namely, [Dy(api)]