Porphyrinylphosphonate-Based Metal–Organic Framework: Tuning Proton Conductivity by Ligand Design
A novel metal–organic framework [Zn3(Ni-H2TPPP)(Ni-H4TPPP)(Ni-H5TPPP)·7(CH3)2NH2·DMF·7H2O]
(where Ni-HxTPPP (x=2,4,5) are partially deprotonated [5,10,15,20-tetrakis(3-(phosphonatophenyl)-porphyrinato(
2-))]nickel(II) species), IPCE-2Ni, with outstanding proton conductivity (1.0V10@2 Scm@1 at 75 8C and 95%
relative humidity) has been obtained. The high concentration of free phosphonate groups and compensating dimethylammonium cations bound by hydrogen bonds in the unique crystal structure of IPCE-2Ni is a key factor responsible for the observed high proton conductivity, which is one order of magnitude higher than for the corresponding MOF based on 5,10,15,20-tetrakis(4-(phosphonatophenyl)porphyrinato(2-))]nickel(II) IPCE-1Ni and comparable with that of leaders among MOFs.