Proton Transport through Robust CPO-27-type Metal Organic Frameworks

In this work we studied the robustness of Ni-CPO-27 and Mg-CPO-27 metal organic frameworks (MOFs) upon cold uniaxial pressing and thermal cycling in dry and wet Ar/H₂. The preparation and operation limits for each material are found to be 225 and 150 MPa and temperatures of 250 and 150 °C for Ni-CPO-27 and Mg-CPO-27, respectively. The electrochemical alternating current conductivity measurements performed as high as 250 °C showed conductivity values ranging from 10^–6 to 10^–8 S/cm, depending on the material, temperature, and atmosphere. The protonic nature of the electrochemical transport phenomena was unambiguously confirmed via proton/deuteron isotopic and transient hydration studies. The study reveals high reproducibility and stability of the electrochemical measurements upon cycling in different atmospheres. Meanwhile, the crystallinity of the sample was preserved after the conductivity study and three weeks on stream, which demonstrates the midterm stability and robustness of this MOF