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

Abstract

A siloxane-based hexacarboxylic acid has been prepared and applied in the construction of new hybrid MOF materials.

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

“…The H-bonding O···O distances are 2.582(2) and 2.711(2) Å, consistent with strong hydrogen bonds 51 observed in similar hydrogen bonded organic frameworks built from polycarboxylic acids. 52,53 The proligand L1-H2 was then treated with LiNO3 and LiOH (1:1:1 molar ratio) under solvothermal conditions in DMF and MeOH (2:1 ratio). A colorless crystalline solid was formed, which was shown by X-ray diffraction to be [Li4(L1)2(H2O)(DMF)2] (IMP-22, where IMP is short for Imperial College London).…”

Hydrophobic, amorphous metal–organic network readily prepared by complexing the aluminum ion with a siloxane spaced dicarboxylic acid in aqueous medium

“…Although the siloxane linkage is present in materials such as zeolites, mesoporous silica, and Polyhedral Oligomeric Silsesquioxane (POSS) hybrids, their use for MOF construction did not trigger a general interest of the scientific community. While Davies et al . synthesized and used as ligands hexa(4‐carboxyphenyl)disiloxane molecules, we tried to use a longer and more flexible dicarboxylic acid, 1,3‐bis(carboxypropyl)tetramethyldisiloxane, as a ligand for metals or for the construction of more complex structures …”

Trisiloxane-centred metal–organic frameworks and hydrogen bonded assemblies

“…[7][8][9] More recently we have shown how linkers with disiloxane backbones, such as hexakisIJ4carboxyphenyl)disiloxane (R 3 Si-O-SiR 3 , R = p-C 6 H 4 COOH), can be used to prepare novel porous 3D coordination polymers that may loosely be described as hybrid MOF-zeolite systems (the siloxane Si-O-Si linkage being ubiquitous in zeolites). 10 Installing siloxane linkages in MOFs may impart several advantageous properties including low chemical reactivity, high thermal stability, hydrophobicity, and enhanced water stability. [10][11][12] In an extension to this earlier work, we now report upon the preparation and application of a hexacarboxylic acid with a trisiloxane backbone, R 3 Si-O-SiMe 2 -O-SiR 3 (R = p-C 6 H 4 COOH), L-H 6 .…”

“…10 Installing siloxane linkages in MOFs may impart several advantageous properties including low chemical reactivity, high thermal stability, hydrophobicity, and enhanced water stability. [10][11][12] In an extension to this earlier work, we now report upon the preparation and application of a hexacarboxylic acid with a trisiloxane backbone, R 3 Si-O-SiMe 2 -O-SiR 3 (R = p-C 6 H 4 COOH), L-H 6 . Extension of the siloxane moiety to in-corporate a central tetrahedral dimethylsilyl functionality leads to a U-shaped Si-O-Si-O-Si backbone in L-H 6 which contrasts with the approximately linear Si-O-Si backbone in the previously reported disiloxane.…”

“…Extension of the siloxane moiety to in-corporate a central tetrahedral dimethylsilyl functionality leads to a U-shaped Si-O-Si-O-Si backbone in L-H 6 which contrasts with the approximately linear Si-O-Si backbone in the previously reported disiloxane. 10 The resultant change in the disposition of the six benzoic acid groups on the linker backbone is reflected in the unique structural forms observed in the hydrogen-bonded assembly of L-H 6 and its coordination complexes.…”