A new porphyrin-based microporous MOF, {Mn(II)0.5[Mn(II)4Cl(Mn(III)Cl-ttzpp)(2)(H2O)(4)]}center dot(DEF)(20)center dot(CH3OH)(18)center dot(H2O)(12) (UTSA-57), has been constructed from {5,10,15,20-tetrakis[4-(2,3,4,5-tetrazolyl)phenyl]porphyrinato} manganese(III) chloride as the metalloligand. The MOF adopts the rare scu topology with one-dimensional square nanotube-like channels of about 20 angstrom. UTSA-57a exhibits permanent porosity and displays moderately high performance for C2H2/CH4 separation at room temperature.