The new porphyrin-based tetraphosphonic acid (Ni-H8TPPP) was employed in the synthesis of four isostructural MOFs of composition [M(Ni-H6TPPP)(H2O)], denoted CAU-29 (M = Mn, Co, Ni, Cd). Ni-CAU-29 was thoroughly characterized regarding its thermal and chemical stability as well as for proton conductivity.