Prospects of monolithic MIL-MOF@poly(NIPAM)HIPE composites as water sorption materials

• Monolithic shaping of MOFs with cross-linked poly(N-isopropyl acrylamide) (NIPAM).
• Poly(NIPAM) as oil–water high internal phase emulsion (HIPE) foam.
• MIL-MOFs in composites with poly(N-isopropyl acrylamide)HIPE, poly(NIPAM)HIPE.
• MIL@poly(NIPAM)HIPE can be loaded with up to 92 wt% of the MIL component.
• Composites tested as water sorbents for water uptake capacity.

Monolithic shaping of metal-organic frameworks (MOFs), which are normally received as microcrystalline powder is crucial for possible applications of MOFs. Three members of the MIL-family (MIL-100(Fe), MIL-100(Cr) and MIL-101(Cr)), known as water stable porous coordination polymers, were embedded into a macroporous oil–water (o/w) high internal phase emulsion (HIPE) foam, based on cross-linked poly(N  -isopropyl acrylamide) (NIPAM). Pre-polymerization of the HIPE emulsions before adding the MIL-MOF powders was an indispensable step in synthesizing highly porous composites, thus, minimizing pore blocking effects. The larger the pores and the higher the surface area of the MIL the less pronounced were pore blocking effects upon composite formation. These composite materials (MIL@poly(NIPAM)HIPE, in short MIL@NIPAM) could be loaded with up to 92 wt% of the MIL component (followed and verified by powder X-ray diffractometry, infrared spectroscopy and scanning electron microscopy). MIL@NIPAM composites show higher water vapor uptakes in comparison to the native HIPE material so that MIL@NIPAM composites could be used as monolithic water sorbents for heat transformation applications. For MIL-101(Cr)@NIPAM the water uptake of up to 0.4 g/g occurs with the typical S-shaped isotherm in the range of 0.3 < P∙P0−1 < 0.5.

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