The control of MOF flexibility through choice of metal is particularly convenient when coupled with the possibility of continuously varying the metallic composition in a mixed-metal MOF -whether during the synthesis or through postsynthetic metal exchange. A clear and comprehensive example of this is the investigation, by Ehrling et al., of the family of switchable MOFs M 2 (2,6-ndc) 2 (dabco), also named DUT-8(M), with M = Ni or Co. While the nickel-based DUT-8 is highly flexible, showing a gate-opening transition at low pressure upon nitrogen adsorption, its cobalt counterpart remains rigid in a closed pore phase. tial substitution of nickel with cobalt allows for a gradual tuning of the gate opening pressure in DUT-8(Co x Ni 1-x ), in the range of p/p 0 from 0.1 to 0.75 (as depicted in Figure ). Through the combination of several experimental techniques, including EPR spectroscopy, the authors demonstrated the coexistence of Ni/Ni, Co/Ni, and Co/Co paddle wheel SBUs in the material. Furthermore, DFT calculations were able to link the change in gate opening pressure with the activation energy of the structural transition.