Solvent hydrolysis and templating effects in the synthesis of metal–organic frameworks

Abstract

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...

Unprecedented Sulfone‐Functionalized Metal–Organic Frameworks and Gas‐Sorption Properties

“…Given the fact that it is generally difficult to completely formulate the exact composition of all guest molecules in highly porous MOFs and also that dimethylammonium cations, (CH 3 ) 2 NH 2 + , are formed in situ upon heating of DMF, [14] it is natural to consider these as charge balancing cations, leading to an overall charged balanced formula [(CH 3 ) 2 …”

Structural variety in ytterbium dicarboxylate frameworks and in situ study diffraction of their solvothermal crystallisation

“…hydrolysis of DMF in the water-rich solvent with prolonged reaction time, as it is well known that decomposition of DMF occurs in water to give formic acid and dimethylamine. 37 This effect has been noted before in the synthesis of other MOFs, 38 and a similar situation was reported in the formation of the gadolinium analogue of (3), although in that work HCl was used in the synthesis. 36 Replacement of 1,4-benzenedicarboxylic acid by 2,6-naphthalene-dicarboxylic acid in the DMF-rich solvent yields [Yb 2 IJNDC) 3 IJH 2 O) 4 ]·2DMF (4), a material that has an isoreticular structure to (2).…”

Hydrothermal Synthesis, Crystal Structure of Four Novel Complexes Based on Thiabendazole Ligand

“…It is worth noting that the formate anion was generated by in situ hydrolysis of DMF. [22][23][24][25][26][27] Therefore, the coordinated BTC ligands adopt monodentate mode and with {HCO 2 } − anions bridge the Zn II ions into a 1D double-chain. As shown in Figure 9, the adjacent chains are connected through weak N-H···O hydrogen bonds from N-H of TBZ together with carboxylic O atom of BTC (N6-H6···O6, N2-H2···O7).…”