Hydrothermal Green Synthesis of a Robust Al Metal-Organic-Framework Effective for Water Adsorption Heat Allocations

To minimize the huge global energy consumption for cooling and heating, adsorption-based heat allocation devices operating with an "adsorbent–water" working pair have received great interest over the last decades. Herein, we report scalable green synthesis of an Al-based metal–organic framework (Al-MOF) in water built from the assembly of inorganic Al helix chains linked to pyridine dicarboxylate linkers that delimits a three-dimensional structure proven to be isoreticular to CAU-10H and denoted as CAU-10pydc. This channel-like MOF exhibits attractive water sorption properties with an S-shaped adsorption isotherm associated with a major water uptake in the range of P/P° = 0.015–0.17 and a good working capacity (0.31 mLH2O mL–1MOF) under low-temperature cooling conditions of the adsorption-driven heat allocation system (Tevaporator(ev) = 5 °C, Tadsorption(ads) and Tcondensation(con) = 30 °C, and Tdesorption(des) = 80 °C), along with exceptional coefficient of performances for both cooling (0.79) and heating (1.72) together with a useful and sustainable heat source accessible from a solar source and good specific heat capacity (212.9 kWh m–3MOF) and heat storage capacity (273.5 kWh m–3MOF). The molecular adsorption mechanism was finally investigated computationally demonstrating the predominant role played by the formation of hydrogen-bonding between water molecules and the hydroxyl functionality of the MOF.