Structural regulation strategy for Dy-MOFs based on [Qn+][Dy(β-diketonate)4-]n (Qn+ = Et3NH+, Et4N+, R-H2MPPA2+)

In this study, [Qn+][Dy(β-diketonate)4-]n (β-diketonate = Hfac, Hbtfa, Hdbm; n = 1, Q+ = Et3NH+, Et4N+; n = 2, Q2+= R-H2MPPA2+) was used to regulate the hydrolysis process of DyIII ions to generate different secondary building units (SBUs). The SBUs were further connected with fumaric acid ligands, exhibiting diverse coordination modes. Five dysprosium-based metal–organic frameworks (Dy-MOFs; 1–5) with various structural connections and topologies were synthesized. When cations in [Qn+][Dy(β-diketonate)4-]n were Et3NH+ and the anions changed from [Dy(fac)4]- to [Dy(dbm)4]- and [Dy(btfa)4]-, three SBUs (C2v Dy1O8, D2d Dy2O8 in 1; C2v Dy1O8 in 2; C4v Dy1O9 in 3) were formed. When anions in [Qn+][Dy(β-diketonate)4-]n were [Dy(btfa)4]- and the cations changed from Et3NH+ to Et4N+ and R-H2MPPA2+, four SBUs (C4v Dy1O9 in 3; Cs Dy1O9, D3h Dy2O9 in 4; D4d Dy1O8 in 5) were formed. Further magnetic characterization indicated that 2, 3, and 4 exhibited antiferromagnetic behavior, while 1 and 5 exhibited ferromagnetic properties. The alternating-current magnetic susceptibilities of 1 and 5 exhibited significant frequency and temperature dependence. The Cole–Cole plot of 1 and 5 displayed a semicircular shape, and the effective energy barrier and relaxation time were 77.54 K and 3.20 × 10–8 s and 6.8 K and 7.50 × 10–5 s for 1 and 5, respectively.