Studies on the structural diversity of MOFs containing octahedral siloxane-backboned connectors

Four metal–organic frameworks containing hexatopic connectors have been prepared and structurally characterised: [Cd3(L)(DMA)2(H2O)2] (IMP-28), [Ce2(L)(DMF)2(H2O)2] (IMP-29), [Y2(L)(DMF)2(H2O)2] (IMP-30), and [Zn2(L-H2)(4,4′-bipy)2] (IMP-31). All the MOFs have been constructed using the hybrid inorganic–organic siloxane linker hexakis(4-carboxyphenyl)disiloxane (L-H6). In each case, discrete metal-based nodes are cross-linked by the octahedrally disposed connector to afford 3D polymeric structures. The underlying nets in these MOFs have been evaluated through deconstruction of their crystal structures and subsequent topological analysis. Examples of MOFs built from hexatopic linkers, and especially those with octahedral predispositions such as in L, remain scarce and the topologies ascribed to some of these MOFs are unique.</p

Siloxane-based linkers in the construction of hydrogen bonded assemblies and porous 3D MOFs

A siloxane-based hexacarboxylic acid (L1-H6) has been prepared and applied in MOF construction. L1-H6 itself crystallizes as an unusual interpenetrated 3D hydrogen-bonded framework. Reaction of L1-H6 with Zn(II) gave IMP-18 – a 3D MOF incorporating Si–O–Si functionality. Cleavage of L1-H6 gives a silanol-based triacid which is shown to give a coordination polymer (IMP-19) with Zn(II)

Trisiloxane-centred metal-organic frameworks and hydrogen bonded assemblies

A hexacarboxylic acid with a trisiloxane backbone (L-H6) has been prepared and applied in MOF construction. L-H6 itself crystallizes as an unusual 2D hydrogen-bonded network. Reaction of L-H6 with Mn(ii) gave IMP-20 and with Zn(ii) gave IMP-21: both are 3D MOFs incorporating Si-O-Si-O-Si linkages.</p

Metal-organic frameworks constructed from Group 1 Metals (Li, Na) and silicon-centered linkers

A series of ‘light metal’ MOFs containing SBUs based on Li+ and Na+ cations have been prepared using the silicon-centered linkers MexSi(p-C6H4CO2H)4-x (x = 2, 1, 0). The unipositive charge, small size, and oxophilic nature of the metal cations gives rise to some unusual and unique secondary building units (SBUs), including a 3D nodal structure built from sodium and oxygen ions when using the triacid linker (x = 1). The same linker with Li+ cations generated a chiral, helical SBU, formed from achiral starting materials. 1D rod SBUs are observed for the diacid (x = 2) and tetra-acid (x = 0) linkers with both Li+ and Na+ cations, where the larger size of Na+ compared to Li+ leads to subtle differences in the constitution of the metal node

Metal–Organic Frameworks Constructed from Group 1 Metals (Li, Na) and Silicon-Centered Linkers

A series of “light metal” metal–organic frameworks containing secondary building units (SBUs) based on Li⁺ and Na⁺ cations have been prepared using the silicon-centered linkers Me_<i>x</i>Si­(<i>p</i>-C₆H₄CO₂H)_4‑<i>x</i> (<i>x</i> = 2, 1, 0). The unipositive charge, small size, and oxophilic nature of the metal cations give rise to some unusual and unique SBUs, including a three-dimensional nodal structure built from sodium and oxygen ions when using the triacid linker (<i>x</i> = 1). The same linker with Li⁺ cations generated a chiral, helical SBU, formed from achiral starting materials. One-dimensional rod SBUs are observed for the diacid (<i>x</i> = 2) and tetra-acid (<i>x</i> = 0) linkers with both Li⁺ and Na⁺ cations, where the larger size of Na⁺ compared to Li⁺ leads to subtle differences in the constitution of the metal nodes