By utilizing the 2-hydroxyisophthalic acid (H(3)ipO) ligand, 2D metal-organic frameworks (MOFs) featuring rare O-phenol-bridged [Ln(2)]-magnetic building blocks (MBBs), [Ln(2)(ipO)(2) (DMF)(H2O)] [Ln = Gd (1), Dy (2); DMF = N,N-dimethylformamide], were rationally designed and synthesized. When the reaction solvents that behave as terminal ligands were changed, the coordination geometries of Ln(III) ions and the arrangement fashion of [Ln(2)]-MBBs for these MOFs were modified accordingly. Another type of 2D MOF of [Ln(2)(ipO)(2)(H2O)(4)]center dot 2H(2)O [Ln = Gd (3), Dy (4)] was thus obtained. MOFs 1 and 3 exhibited favorable magnetocaloric effect, whose maximum -Delta S-m values reach 30.0 and 31.7 J kg(-1) K-1, respectively. None of the single-molecule-magnet (SMM) behavior was observed in 2. However, from 2 to 4, the change of the terminal coordinated solvents brought obvious improvement of the magnetic properties. MOF 4 showed interesting relaxation behavior, in which dual relaxation was only visible under weak direct-current fields, and its highest effective energy barrier (U-eff) reached up to 243 K Ab initio calculations revealed the tuning mechanism of the terminal coordinated solvents. Their change optimized the arrangements of the magnetic axis of the Dy-III centers in both each MBB and the whole framework, thus improving the magnetic anisotropy and magnetic interactions of the system. Significantly, within the [Dy-2]-MBBs of 4, the angle made by the individual magnetic axis and Dy...Dy' line is nearly 0 degrees. This case favoring a high SMM performance not only was scarcely achieved in discrete {Ln(2)}-SMMs with numerous members but also has never been observed in any MBB-based MOFs as far as we know.