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

Abstract

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.