Promotion of Proton Conductivity by Encapsulation of Metal‐Organic Polyhedra in Metal‐Organic Frameworks

Abstract A Zr‐based metal‐organic polyhedron (MOP) was self‐assembled in a porous MOF host, DUT‐68, successfully to synthesize MOP‐1@DUT‐68. The MOP guest (MOP‐1) has a diameter of about 20 Å, larger than that of the square windows (pore sizes of ∼14 Å) of DUT‐68 but smaller than that of the rhombicuboctahedral cage (27.7 Å), which means that the migration and leaching of MOP‐1 could be effectively prohibited if MOP‐1 is encapsulated in the MOF′s cavities. The proton conductivity of MOP‐1@DUT‐68 is 1.14×10 −3 S cm −1 (at 80 °C under 98 % relative humidity), which is three orders of magnitude higher than that of DUT‐68. Compared with MOP‐1⊂DUT‐68, which was synthesized by impregnation, MOP‐1@DUT‐68 is more prone to form faster proton‐conduction pathways and thus provides higher proton conductivity.