Hydrophilic porous materials are recognized as very promising materials for water-sorption-based energy storage and transformation. In this study, a porous, zeolite-like aluminophosphate with LTA (Linde Type A) topology is inspected as an energy-storage material. The study is motivated by the material's high predicted pore volume. According to sorption and calorimetric tests, the aluminophosphate outperforms all other zeolite-like and metal-organic porous materials tested so far. It adsorbs water in an extremely narrow relative-pressure interval (0.10 < p/p 0 < 0.15) and exhibits superior water uptake (0.42 g g −1 ) and energy-storage capacity (527 kW h m −3 ). It also shows remarkable cycling stability; after 40 cycles of adsorption/desorption its capacity drops by less than 2%. Desorption temperature for this material, which is one of crucial parameters in applications, is lower from desorption temperatures of other tested materials by 10-15 °C. Furthermore, its heatpump performance is very high, allowing efficient cooling in demanding conditions (with cooling power up to 350 kW h m −3 even at 30 °C temperature difference between evaporator and environment). On the microscopic scale, sorption mechanism in AlPO 4 -LTA is elucidated by X-ray diffraction, nuclear magnetic resonance measurements, and first-principles calculations. In this aluminophosphate, energy is stored predominately in hydrogen-bonded network of water molecules within the pores.

Complementary techniques elucidate water–framework interactions in different states of dehydration, two of which have not been observed before.