Series of Porous 3-D Coordination Polymers Based on Iron(III) and Porphyrin Derivatives

A new series of 3-D coordination polymers based on iron(III) and nickel(II) tetracarboxylate porphyrin (Ni-TCPP) have been produced using solvothermal conditions. MIL-141(A) solids (MIL stands for Material from Institut Lavoisier), formulated Fe(Ni-TCPP)A•(DMF)_x (A = Li, Na, K, Rb, Cs, DMF = N,N-dimethylformamide, x ∼ 3), are built up from three anionic interpenetrated PtS-type networks charge-balanced by alkali cations (A) entrapped inside the pores. MIL-141(A) thus includes three types of cations, two of which may act as coordinatively unsaturated metal sites (Ni²⁺ and A⁺). These solids all present a permanent porosity with a reasonably high surface area (S_BET = 510–860 m² g^–1) as well as some structural flexibility toward adsorption/desorption processes, modulated in both cases by the nature of A. Thermally Stimulated Current (TSC) measurements indicated that alkali cations are rather homogeneously distributed within the pores, while their interaction with the framework is stronger in MIL-141(A) than in the analogous cation-containing Faujasites X and Y zeolites. Finally, high pressure adsorption isotherms of N₂ and O₂ were measured. Whereas alkali ion-containing zeolites adsorb selectively N₂ toward O₂, the opposite is observed for MIL-141(A). This result is interpreted in light of the TSC data and the possible preferential interaction of the porphyrinic linker with O₂.