Efficient use of energy for cooling applications is a very important and challenging field in science. Ultra-low temperature actuated ( T driving < 80 °C) adsorption-driven chillers (ADCs) with water as the cooling agent are one environmentally benign option. The nanoscale metal-organic framework [Al(OH)(C 6 H 2 O 4 S)] denoted CAU-23 was discovered that possess favorable properties, including water adsorption capacity of 0.37 g H2O / g sorbent around p / p 0 = 0.3 and cycling stability of at least 5000 cycles. Most importantly the material has a driving temperature down to 60 °C, which allows for the exploitation of yet mostly unused temperature sources and a more efficient use of energy. These exceptional properties are due to its unique crystal structure, which was unequivocally elucidated by single crystal electron diffraction. Monte Carlo simulations were performed to reveal the water adsorption mechanism at the atomic level. With its green synthesis, CAU-23 is an ideal material to realize ultra-low temperature driven ADC devices.

Great current progress in the materials science offers an enormous choice of novel adsorbents which may be promising for transformation and storage of low temperature heat, e.g. from renewable heat sources. This paper gives an overview of recent trends and achievements in this field. We consider possible optimization of zeolites by dealumination, further development on aluminophosphates, composites salt in porous host matrice and metal-organic frameworks which are currently receiving the largest share of scientific attention. The particular attention is focused on the chemical nano-tailoring and tunable adsorption behavior of these materials to satisfy the demands of appropriate heat transformation cycles. We hope that this review will give new impact on target-oriented research on the novel adsorbents for heat transformation and storage

The solid-solution mixed-linker approach, where a linker is partially replaced by a similar one under retention of the isoreticular metal–organic framework (MOF) structure, offers an easy and inexpensive way to fine-tune MOF properties to design tailored compounds. A total of 10 aluminum mixed-linker MOFs, [Al­(OH)­(X) a (Y)1–a ] (X = IPA, isophthalate; Y = FDC, 2,5-furandicarboxylate) spanning between the isostructural MOFs CAU-10-H (a = 1) and MIL-160 (a = 0), were synthesized by employing different ratios of the aforementioned linkers. CAU-10-H and MIL-160 have been reported as highly promising materials for cycling water sorption for heat transformation applications. A detailed characterization with a focus on the changes in the sorption properties for water vapor showed that the hydrophilicity is readily and easily tuned through the mixed-linker approach between the limits of MIL-160 and CAU-10-H. An increasing fraction of IPA shifts the steep increase in the S-shaped water adsorption isotherm in small steps from p/p 0 = ∼0.05 for MIL-160 to p/p 0 = ∼0.18 for CAU-10-H. Higher coefficient of performance (COPH) values for the mixed-linker materials over MIL-160 illustrate the well-balanced hydrophobicity/hydrophilicity of the former under the exemplary calculation conditions.

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MIL-53(Al)-TDC shows good hydrothermal stability and desirable water sorption properties for heat transformation applications.

Metal–organic frameworks (MOFs) currently receive high interest for cycling water adsorption applications like adsorption heat transformation for air-conditioning purposes. For practical use in adsorption heat pumps (AHPs), the microcrystalline powders must be formulated such that their high porosity and pore accessibility are retained. In this work, the preparation of millimeter-scaled pellets of MIL-160­(Al), Al-fumarate (Basolite A520), UiO-66­(Zr), and Zr-fumarate (MOF-801) is reported by applying the freeze granulation method. The use of poly­(vinyl alcohol) (PVA) as a binder reproducibly resulted in highly stable, uniformly shaped PVA/MOF pellets with 80 wt % MOF loading, with essentially unchanged MOF porosity properties after shaping. The shaped pellets were analyzed for the application in AHPs by water adsorption isotherms, over 1000 water adsorption/desorption cycles, and thermal and mechanical stability tests. Furthermore, the Al-fum pellets were applied in a fixed-bed, full-scale heat exchanger, yielding specific cooling powers from 349 up to 431 W/kg (adsorbent), which outperforms the current commercially used silica gel grains in AHPs under comparable operating conditions.

No deliquescence, cycle stability, increased water uptake over a neat MOF and LiCl at low humidity, and high coefficient of performance.

Cyclic physical adsorption and desorption processes on porous materials can be used for the conversion of heat in heat transformation processes, which is the working principle in adsorption heat pumps (AHPs). Environmentally benign water with its high enthalpy of evaporation is the working fluid of choice in AHPs. Metal‐organic frameworks, MOFs can adsorb large amounts of water or methanol, up to their own weight. MOFs could be alternative materials to silica gels, zeolites, or aluminum phosphates for low‐temperature heat transformations in AHPs.