Nanoporous lanthanide-carboxylate frameworks based on 5-nitroisophthalic acid

The reactions of lanthanide nitrates with 5-nitroisophthalic acid (ab. 5-H2nip) in DMF and ethanol (1 : 1) mixed solution gave rise to three nanoporous lanthanide polymers, {[Ln2(5-nip)3(DMF)4](DMF)2}n (Ln = Nd (1), Dy (2), Ho (3), 5-nip = 5-nitroisophthalate). Single-crystal X-ray diffraction analyses reveal that they are isomorphous and feature three-dimensional metal–organic frameworks with two-dimensional intersecting channels occupied by guest DMF molecules constructed from the linkage of dimer Ln2C6O12 SBUs and 5-nip ligands. The guest DMF molecules can be reversibly removed from 2 as identified using TGA-DSC and PXRD. The heat of adsorption of the guest-free sample of 2 with DMF was measured with a value of 10.3 kJ mol−1 by an RD496-III type microcalorimeter. In addition, the photoluminescent property of 2 was investigated.