(A) Line structures of BDC, BODCA, and a representation of the cross-section of their volumes of revolution viewed down the main molecular axes. The diameters of the two rotors (d) are 5.6 Å. (B) Results from energy scans illustrating half a period (180°) of the sixfold degenerate energy potential of BODCA-MOF with the ground-state (GS) and transition-state (TS) structures viewed down the BCO-carboxylate linkage [black squares B3LYP/6–31G(d); blue circles MP2/6–31G(d); red rhombs ωB97xd/6–311+G(d); green triangles, M062X/6–311+G(d)]. The rotational angle is defined by the dihedral formed between the pane of the carboxylate and the plane of the BCO blade. GS geometries have dihedral angles of 0, 60, 120, etc.; the TS have dihedral angles of 30, 90, 150, etc. High-temperature measurements with RT > Ea are expected to reflect diffusional rotation, and low-temperature measurements with RT < Ea are expected to occur by a site-exchange mechanism.