Hydrolysis of the DMF or DEF solvent influences the nature of the product observed in the reaction between zinc(II) nitrate and 1,4-benzenedicarboxylic acid, with dialkylammonium cations able to template the formation of anionic networks.Coordination networks, or metal-organic frameworks (MOFs) are currently attracting a tremendous amount of interest. 1,2 This is largely a result of their potential for porosity, and the implications of this in applications such as gas storage. 3,4 Some of the most spectacular results in this area have arisen from the Yaghi group. 5-8 They have reported a number of interesting structures, and impressive adsorption properties for compounds such as [Zn 4 (m 4 -O)(m-bdc) 3 ] (bdc 22 5 1,4-benzenedicarboxylate, terephthalate), which they refer to as MOF-5. Although the effectiveness of this material in hydrogen absorption has recently been queried, 9 MOF-5 and related compounds are currently receiving considerable attention within the porous material field. [10][11][12] From a chemical perspective, the zinc-bdc 22 system is far from straightforward. [Zn 4 (m 4 -O)(m-bdc) 3 ] can be prepared from Zn(NO 3 ) 2 ?6H 2 O and H 2 bdc under solvothermal conditions 13 or at room temperature. 14 In addition to [Zn 4 (m 4 -O)(m-bdc) 3 ], a number of other compounds have been prepared from Zn(NO 3 ) 2 ?6H 2 O and H 2 bdc. [15][16][17] In this paper we report how the presence of water in the solvent is crucial in influencing the product from the reaction between Zn(NO 3 ) 2 ?6H 2 O and 1,4-benzenedicarboxylic acid in either DMF or DEF.When Zn(NO 3 ) 2 ?6H 2 O and H 2 bdc were heated in fresh DEF at 95 uC for 3 h, small colourless crystals precipitated from the solution. These were shown to be [Zn 4 (m 4 -O)(m-bdc) 3 ]?3DEF 1 (i.e. solvated MOF-5) by a combination of X-ray single-crystal and powder diffraction experiments, the latter of which produce identical results to those simulated from the previously reported crystal structure. 5 When Zn(NO 3 ) 2 ?6H 2 O and H 2 bdc were heated under the same conditions, in DEF that had been in the laboratory for several weeks, small colourless crystals were again isolated. However, in this case, the product was shown by a combination of X-ray single-crystal and powder diffraction experiments to be exclusively the previously unreported compound [NH 2 Et 2 ] 2 [Zn 3 (mbdc) 4 ]?2.5DEF 2.The structure of 2 is based on bdc 22 anions bridging between linear Zn 3 (m-O 2 CR) 6 secondary building units (SBUs). The central Zn(1) atom has a distorted octahedral geometry, and is k 1 -coordinated to six carboxylates. The two symmetry-related peripheral Zn(2) atoms exhibit distorted tetrahedral geometry, and are each k 1 -coordinated to four carboxylates. Three of these groups bridge to Zn(1), though one adopts the m-k 1 O,k 1 Ocoordination mode rather than the more common m-k 1 O,k 1 O9-mode employed by the other two. The six bridging carboxylates radiate from the Zn 3 (m-O 2 CR) 6 SBU at approximately 60u angles, leading to the construction of a layer structure with tri...

The products isolated from the reaction between Cd(NO3)2 x 4H2O and 1,4-benzenedicarboxylic acid (H2bdc) in DMF are very dependent on the conditions. At 115 degrees C, the reaction gives [Cd(bdc)(DMF)]infinity, which has a three-dimensional network structure, whereas at 95 degrees C, 1 is formed alongside [Cd3(bdc)3(DMF)4]infinity 2, which has a two-dimensional network structure. When the reaction is carried out under pressure, it yields [Cd3(bdc)3(DMF)4]infinity 3, which is a supramolecular isomer of 2. The structure of 3 differs from that of 2 regarding the way the Cd3(O2CR)6 units are interlinked to form layers. When the reaction was carried out in DMF that had undergone partial hydrolysis, the only isolated product was [(NMe2H2)2[Cd(bdc)2] x 2DMF]infinity 4. Compound 4 has a three-dimensional triply-interpenetrated diamondoid structure, with dimethylammonium cations and DMF molecules included within the pores. The reaction between Cd(NO3)2 x 4H2O and H2bdc in DEF gave [Cd(bdc)(DEF)]infinity 5, regardless of the solvent quality. Compound 5 has a three-dimensional network structure. The reaction of Cd(NO3)2 x 4H2O and 1,3-benzenedicarboxylic acid (H2mbdc) in DMF gave [Cd(mbdc)(DMF)]infinity 6 which has a bilayer structure. The thermal properties of the new materials have been investigated, and the coordinated DEF molecules from 5 can be removed on heating to 400 degrees C without any change in the powder X-ray diffraction pattern. The H2 sorption isotherm for the desolvated material shows marked hysteresis between adsorption and desorption, and less adsorption than predicted by simulations. Kinetic data indicate that the hysteresis is not due to mass transfer limitations, and the most likely explanation for this behaviour lies in partial collapse of the framework to an amorphous phase under the conditions of activation.