Solvent-Induced Magnetic Properties of a Series of Dy-Based MOFs from Two Different Precursor Complexes

It is still challenging for Dy-MOFs to modulate the single-molecule magnet (SMM) behavior through guest molecules. Dy-MOFs with different guest molecules, secondary building units, and linkers were synthesized by precursors and bridging carboxylic acid ligands, and the magnetic properties of Dy-MOFs were regulated by guest molecules. These differentiated Dy-MOFs are [Dy2(C9H4Cl2NO)2(L1)2(H2O)(DMA)]n·DMA (MOF-3, L1 = terephthalate), [Dy(C9H4Cl2NO)2(L1)(DMSO)(H2O)]n (MOF-4), [Dy2(C9H4Br2NO)2(L1)2(H2O)(DMA)]n·DMA (MOF-5), [Dy(C9H4Cl2NO)2(L2)(H2O)]n·DMA (MOF-6, L2 = isophthalate), and [Dy(C9H4Cl2NO)2(L2)(H2O)]n·DMF (MOF-7), [Dy(C9H4Br2NO)2(L2)(H2O)]n·DMA (MOF-8). The single-crystal X-ray diffraction showed that MOF-3 and MOF-5 are two-dimensional MOFs with square holes. MOF-4 is a two-dimensional MOF formed by hydrogen–halogen bonds, and MOF-6, MOF-7, and MOF-8 are one-dimensional chains. The magnetic test results show that MOF-4, MOF-6, and MOF-8 show SMM behavior under zero field, and MOF-3 and MOF-5 exhibit field-induced SMM behavior. In the zero field, the effective energy bases of MOF-4, MOF-6, and MOF-8 are 37.09, 19.56, and 15.73 K, and relaxation times τ0 were 4.66 × 10–6, 2.35 × 10–6, and 9.95 × 10–6 s, respectively. This work provides a vivid example of regulating the molecular magnetism of Dy-MOFs and promotes the progress of Dy-MOF crystal engineering.