Metal–organic
frameworks (MOFs) are attracting attention
as potential proton conductors. There are two main advantages of MOFs
in this application: the possibility of rational design and tuning
of the properties and clear conduction pathways given by their crystalline
structure. We hereby present two new MOF structures, ICR-10 and ICR-11,
based on tetratopic phosphinate ligands. The structures of both MOFs
were determined by 3D electron diffraction. They both crystallize
in the P3̅ space group and contain arrays of
parallel linear pores lined with hydrophilic noncoordinated phosphinate
groups. This, together with the adsorbed water molecules, facilitates
proton transfer via the Grotthuss mechanism, leading to a proton conductivity
of up to 4.26 × 10–4 S cm–1 for ICR-11. The presented study demonstrates the high potential
of phosphinate MOFs for the fabrication of proton conductors.