New Polymorphs of Magnesium‐Based Metal–Organic Frameworks Mg 3 (ndc) 3 (ndc = 2,6‐Naphthalenedicarboxylate)

Two new magnesium 2,6‐naphthalenedicarboxylate (ndc) metal–organic frameworks, [Mg 3 (ndc) 3 (dif) 4 ] ( 1 ) (dif = N , N ‐diisopropylformamide) and [Mg 3 (ndc) 3 (dmf) 2 (CH 3 OH)(H 2 O)](dmf) ( 2 = TUDMOF‐3) (dmf = N , N ‐dimethylformamide), have been synthesised under solvothermal conditions from Mg(NO 3 ) 2 · 6H 2 O and pure 2,6‐naphthalenedicarboxylic acid. According to single‐crystal X‐ray crystallographic studies, complex 1 crystallises in the space group P 2 1 / n [ a = 14.769(3) Å, b = 13.325(3) Å, c = 17.998(4) Å, β = 108.67(2)°] and complex 2 in the space group P $\bar {1}$ [ a = 11.1116(11) Å, b = 12.6229(13) Å, c = 17.800(2) Å, α = 88.568(14)°, β = 83.833(13)°, γ = 70.167(11)°]. The structures of compounds 1 and 2 consist of trinuclear magnesium clusters connected to six dicarboxylate ligands; for 2 , the clusters act as distorted octahedral nodes to give a 3D network. In contrast, the trinuclear clusters in 1 act as pseudo‐planar‐hexagonal nodes to give a 2D network assembly. According to nitrogen and hydrogen physisorption measurements at 77 K for compounds 1 and 2 , TUDMOF‐3 has a permanent porosity with a Langmuir surface area of 632 m 2  g –1 , a specific pore volume of 0.21 cm 3  g –1 and a hydrogen storage capacity of 1.23 wt.‐% at 77 K and 1 bar, whereas compound 1 is not porous.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)