MIL-100(Al, Fe) as water adsorbents for heat transformation purposes—a promising application

Abstract

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

Water Sorption Cycle Measurements on Functionalized MIL-101Cr for Heat Transformation Application

“…All the materials showed a distinct hysteresis between adsorption and desorption branches widely known for mesoporous materials. 7,30,33 Unfortunately, this hysteresis somewhat reduces the usable part of the loading lift of the materials.…”

New Group 13 MIL‐53 Derivates based on 2,5‐Thiophenedicarboxylic Acid

“…1 H (600.15 MHz) high-resolution spectra were acquired after a 90°pulse of 1.4 μs with a spinning speed of 62.5 kHz using a commercial 1.3 mm MAS double resonance probe (Bruker). 13 C (100.6 MHz) MAS spectra were obtained with a ramped cross-polarization (CP) [58] experiment where the nutation frequency ν nut on the proton channel was varied linearly by 30 %. The samples were spun at 12.5 kHz in a 3.2 mm MAS triple resonance probe (Bruker).…”

“…As opposed to the as-synthesized sample, the activated compound allows to differentiate several peaks in each of those regions. 27 Al, 1 H, and 13 C NMR spectra present noticeable differences between the as-synthesized and activated Al-MIL-53-TDC. These changes in the spectra are attributed to the structural influence of the DMF on the framework, which is removed upon activation.…”

“…[11,12] These properties render Al-MOFs potential candidates for gas storage and separation or heat transformation processes. [13][14][15][16][17] Beneficial for industrial applications are the facts that Al sources are mostly inexpensive and that aluminum is a light metal of low toxicity. [18] From known Al-MOFs we have seen, that framework topologies strongly depend on linker geometries.…”

Synthesis, Crystal Structure, and Solid-State NMR Investigations of Heteronuclear Zn/Co Coordination Networks — A Comparative Study

“…3,4 The wide structural diversity offered by this class has high potential for various applications including gas storage, 5,6 catalysis, 7 sensoring, 8 gas separation 9 and others, such as heat-transformation applications. [10][11][12][13] They are designed from inorganic building blocks, e.g., metal ions or clusters interconnected by polyfunctional organic ligands.…”