Two calcium pyrene phosphonate frameworks with contrasting dimensionality and porosity

Two new calcium phosphonate metal-organic frameworks (P-MOFs), IEF-33 and IEF-34, have been solvothermally synthesized from a pyrene tetraphosphonate ligand and structurally characterized by single-crystal X-ray diffraction. The two compounds arise from different degrees of ligand hydrolysis and exhibit distinct architectures: IEF-33 forms a 2D layered framework interacting through hydrogen bonds with interlayer water-filled channels, whereas IEF-34 adopts a 3D porous network with 1D channels. Gas sorption measurements demonstrate the permanent porosity of IEF-34, which exhibits a BET surface area of 491 m² g^-1 and a CO₂ uptake of 1.6 mmol g^-1 at 273 K. Both materials show good chemical stability in aqueous and organic media, and moderate thermal stability. In addition, IEF-33 and IEF-34 show strong visible-light absorption with optical band gaps of 2.51 and 2.62 eV, respectively.