Syntheses, Crystal Structures, and Gas Storage Studies in New Three-Dimensional 5-Aminoisophthalate Praseodymium Polymeric Complexes

The hydrothermal reaction of 5-aminoisophthalic acid and praseodymium oxide in different acids results in two new praseodymium coordination polymers, [Pr-2(aiP)(3)(H2O)(2)center dot 3H(2)O}(n) (1) and {Pr-2(HaiP)(2)(aip)(NO3)(2)center dot 8H(2)O}(n) (2) (aip = 5-aminoisophthalate). Complexes 1 and 2 are two distinct three-dimensional metal-organic frameworks constructed from the linkage of rod-shaped praseodymium carboxylate secondary building units and phenyl rings. Both dehydrated coordination frameworks are estimated using a computational method based on Connolly's algorithm, indicating that dehydrated compound 1 cannot host molecules other than water molecules or He, whereas dehydrated compound 2 is able to host molecules with kinetic radii as big as 2.3 angstrom. The potential specific accessible surface of this compound is 792 m(2) g(-1). Meanwhile, N-2 sorption measurements reveal that dehydrated compound 2 having a high 230 cm(3)/g (287 mg/g) N-2 storage capacity at 77 K and 1 atm is in fairly good agreement with our calculation results. Moreover, powder X-ray diffraction measurement results demonstrated that the stable channels of dehydrated compound 2 can reversibly host other small solvent molecules (e.g., water, methanol, and ethanol) and grand canonical Monte Carlo simulation is applied to predict its hydrogen storage capacity.