M = Mn, Zn, Cd. We hypothesized that the central metal ion of the cluster of an MFU-4l framework could govern the opening of the tripodal scaffold for the peripheral sites according to the magnitude of its ionic radius, thereby adjusting the geometry of the peripheral sites and tuning their adsorption properties (Figure ). To synthesize MFU-4l frameworks with a central metal ion other than zinc(II), we conducted solvothermal syntheses using manganese(II) and cadmium(II) salts. These metals were selected because high-spin d Mn II and d 10 Cd II are not subject to a Jahn-Teller distortion and are therefore suitable to reside at the six-coordinate central site with an ideal octahedral geometry. Additionally, the ionic radii of Zn II (0.74 Å), high-spin Mn II (0.83 Å) and Cd II (0.95 Å) are almost evenly spaced with an approximately 0.1 Å difference, allowing for systematic structure-property examinations.