The adsorption/desorption of up to 0.75 g of water vapour per g of the porous MOFs 3D-{M 3 O(X)(H 2 O) 2 [btc] 2 $nH 2 O}, MIL-100 (M ¼ Al, Fe; X ¼ OH, F, btc ¼ benzene-1,3,5-tricarboxylate, trimesate), occurs at small relative pressures of p/p 0 < 0.4 and a comparatively small hysteresis. Together with very good cycle stability, these properties render both MIL-100(Al and Fe) very suitable candidates for thermally driven heat pumps or adsorption chillers.More than 50% of the energy consumption and, simultaneously, the CO 2 emissions of modern buildings originate from air conditioning processes. These are traditionally based on electrically driven, mechanical compression chillers and heat pumps or classical burner systems, respectively. This demand is expected to rise in the future because of increased living standards and global climate change. 1 However, with alternative technologies, less exergetic (that is, closer to equilibrium) forms of energy, even low-temperature waste heat from industrial processes, can be employed for both heating and cooling. Solar heat as driving energy is especially interesting due to the high coincidence of cooling demand and solar irradiation. While multiple working principles for thermally driven heat-pumps can be realised, the evaporation-adsorption method has proven most feasible for this purpose and is briefly described in Fig. 1 and Table 1.The presented process renders cooling applications independent of precious electrical energy. If it is used for heating, the incorporation of environmental heat allows for considerable fuel savings. The coefficient of performance (i.e. the relation between useful and driving heat), power density, cost and operating lifetime of the complete machine are governed by the sorption material and its figures of merit, i.e. porosity, water sorption capacity, hydrophilicity and hydrothermal stability. 2,3 The achievable loading lift and also the required desorption temperature directly depend on the hydrophilicity of the material, i.e., the p/p 0 value at which adsorption occurs

The 3D metal-organic framework (MOF) (3)(infinity){[Ni(3)(mu(3)-btc)(2)(mu(4)-btre)(2)(mu-H(2)O)(2)]. approximately 22H(2)O} is found to be a reversibly dehydratable-hydratable water-stable MOF material with a large loading spread of 210 g/kg as a candidate for solid adsorbents in heat transformation cycles for refrigeration, heat pumping, and heat storage.

JANIAK, C.; Eur. J. Inorg. Chem. 2012, 16, 2625-2634, http://dx.doi.org/10.1002/ejic.201101056 ; Fraunhofer-Inst. Solare Energiesyst., D-79110 Freiburg/Br., Germany; Eng.) -Lindner 34-244

The distinctive water sorption properties of microporous aluminium fumarate (s-shaped isotherm{,} narrow hysteresis{,} loading >0.3 g g-1 at a relative pressure as low as p/p0 = 0.3 under realistic working conditions) permit a large advancement of MOF-based sorption heat transformation processes{,} especially as we demonstrate that the favourable sorption properties are accompanied by an unprecedented cyclic hydrothermal stability. With regard to the application of heat transformation{,} where unhindered heat and mass transfer are crucial for fast ad-/desorption cycles and a high power density{,} the question of proper shaping was also addressed. A 300 [small mu ]m thick{,} polycrystalline{,} thermally well coupled and highly accessible coating of microporous aluminium fumarate was deposited on a metal substrate via the thermal gradient approach{,} and found to be stable for the first 4500 ad-/desorption cycles with water vapour

Sorption-based heat transformation and storage appliances are very promising for utilizing solar heat and waste heat in cooling or heating applications. The economic and ecological efficiency of sorption-based heat transformation depends on the availability of suitable hydrophilic and hydrothermally stable sorption materials. We investigated the feasibility of using the metal-organic frameworks UiO-66(Zr), UiO-67(Zr), H2N-UiO-66(Zr) and H2N-MIL-125(Ti) as sorption materials in heat transformations by means of volumetric water adsorption measurements, determination of the heat of adsorption and a 40-cycle ad/desorption stress test. The amino-modified compounds H2N-UiO-66 and H2N-MIL-125 feature high heat of adsorption (89.5 and 56.0 kJ mol(-1), respectively) and a very promising H2O adsorption isotherm due to their enhanced hydrophilicity. For H2N-MIL-125 the very steep rise of the H2O adsorption isotherm in the 0.1 < p/p0 < 0.2 region is especially beneficial for the intended heat pump application.