Hydrolytic stability in hemilabile metal–organic frameworks

Abstract

Highly porous metal-organic frameworks (MOFs), which have undergone exciting developments over the past few decades, show promise for a wide range of applications. However, many studies indicate that they suffer from significant stability issues, especially with respect to their interactions with water, which severely limits their practical potential. Here we demonstrate how the presence of 'sacrificial' bonds in the coordination environment of its metal centres (referred to as hemilability) endows a dehydrated copper-based MOF with good hydrolytic stability. On exposure to water, in contrast to the indiscriminate breaking of coordination bonds that typically results in structure degradation, it is non-structural weak interactions between the MOF's copper paddlewheel clusters that are broken and the framework recovers its as-synthesized, hydrated structure. This MOF retained its structural integrity even after contact with water for one year, whereas HKUST-1, a compositionally similar material that lacks these sacrificial bonds, loses its crystallinity in less than a day under the same conditions.

Metal–Organic Framework‐Activated Carbon Composite Materials for the Removal of Ammonia from Contaminated Airstreams

“…, b) display the overall morphology of the unimpregnated BPL carbon and STAM-17-OEt, respectively.T he large voids of % 50 mminBPL carbon are clearly visible and allow synthesis of smaller MOF crystals within the carbon. STAM-17-OEt crystals have hexagonal morphology and are usually observed as stacked hexagons with typically % 20 mmdiameter [11]. SEM images and associated copper elemental mapping images of STAM-17-OEt@BPL_1(Figure 2c,d ), STAM-17-OEt@BPL_2(Figure 2e,f), and STAM-17-OEt@BPL_3(Figure 2g,h)v erify the fairly even distribution of copper throughout the carbon.…”

“…We recently reported the structure of STAM-17-OEt and highlighted its exceptional hydrolytic stability and ability to remove ammonia from both dry and humid airstreams. [11] In this study,wereport the synthesis of three novel MOF-carbon composite materials containing STAM-17-OEt and BPL activated carbon. BPL is an unimpregnated coal-based carbon, which is representative of activated carbons that have been used to prepare impregnated carbons such as those often used in respiratory protection.…”

“…[12] STAM-17-OEt, like other MOFs,i sm icroporous,t hough has as urprisingly low surface area of 58 m 2 g À1 . [11] Thel ow porosity in STAM-17-OEt is due to its switchable structure, where upon activation the pores in STAM-17-OEt become constricted by the change in the coordination environment of the copper paddlewheels.T his constriction consequently impacts the porosity,t hough the low surface area observed for STAM-17-OEt is not representative of the materials overall gas adsorption capability.Asignificant drop in the porosity of the carbon upon incorporation of the MOF would provide further evidence that STAM-17-OEt is inside the carbon, due to partial pore-blocking by STAM-17-OEt crystals.T he surface areas of the composites do fall inbetween those of the MOF and carbon alone,w here the higher the MOF content, the lower the surface area (Table 1). Thegreatest loss of porosity is observed in the highest loading Dynamic vapour sorption (DVS) studies using either cyclohexane or water vapours were performed on the materials.C yclohexane is known to adsorb on the carbon but not the MOF (due to its relatively small pore size) and while water vapour adsorbs on both, the resulting isotherms are very different in shape.I ne ither case,p re-activated samples were exposed to increasing levels of relative pressure and the associated uptake was measured at each point.…”

2D Oligosilyl Metal–Organic Frameworks as Multi‐state Switchable Materials

“…Communications 766 www.angewandte.org MOFs) where the IR feature is attributed to an ew asymmetric COO stretch. [34][35][36] In the case of CuBDC,t he open axial metal sites associate with oxygen atoms in carboxyl groups of neighboring paddlewheels.The IR spectral changes for desolvated Cu(lin-Si 2 )are consistent with reported results in CuBDC and suggest the presence of as imilar bridging carboxyl group between adjacent Cu paddlewheels. [36] The thermally-activated Cu(lin-Si 2 )i sl argely amorphous by PXRD,which is consistent that the removal of the coordinating ligand leads to facile shifting of the individual sheets.The flexibility of the organosilicon linker may further disrupt crystalline packing in the absence of ad irecting solvent.…”

Metal–Organic Framework‐Activated Carbon Composite Materials for the Removal of Ammonia from Contaminated Airstreams

“…[11] In this study,wereport the synthesis of three novel MOF-carbon composite materials containing STAM-17-OEt and BPL activated carbon. [11] In this study,wereport the synthesis of three novel MOF-carbon composite materials containing STAM-17-OEt and BPL activated carbon.…”