Assembly of three Nd(iii) 2,6-naphthalenedicarboxylates (ndc2−) 3D coordination polymers based on various secondary building units (SBUs): structural diversity and gas sorption properties

Abstract

Three porous neodymium(III) coordination polymers (CPs) with the chemical formulas of [Nd(ndc)_1.5(DMF)₂]·DMF·CH₃OH·H₂O (1), [Nd(ndc)_1.5(DMA)_0.5(H₂O)]·1.5DMA (2), and [Nd(ndc)_1.5(H₂O)₂]·2DMA (3) (ndc²⁻ = dianion of 2,6-naphthalenedicarboxylic acid; DMF = N,N-dimethylformamide, DMA = N,N-dimethylacetamide) based on Nd(III) ions have been synthesized using 2,6-naphthalenedicarboxylate (ndc²⁻) as a linker and they were structurally determined by single-crystal X-ray diffraction analysis. In compound 1, two Nd(III) ions are bridged by ndc²⁻ ligands with three kinds of coordination modes: bis-bidentate bridging, bis-bidentate chelate, and bis-bidentate chelate and bridging, to generate a [Nd₂(O₂CR)₆] dinuclear moiety, which serves as an octahedral secondary building unit (SBU) to produce a three-dimensional (3D) non-interpenetrating open metal–organic framework (MOF). In compounds 2 and 3, the Nd(III) ions are bridged by ndc²⁻ ligands with a bis-bidentate bridging coordination mode for 2 and bis-bidentate bridging and bis-bidentate chelate coordination modes for 3 to generate rod-shaped SBUs, producing 3D non-interpenetrating MOFs with 1D rhombic and triangular channels for 2 and 3, respectively. The gas (N₂) sorption measurements for compounds 1–3 have been carried out and reveal that the BET surface areas of the solvent-free frameworks are estimated to be 149.62, 78.12 and 57.91 m² g⁻¹ for 1, 2 and 3, respectively.