MIL-101(Cr)/calcium chloride composites for enhanced adsorption cooling and water desalination

Abstract

The adsorption capacity of adsorbent materials at low relative pressure range is a crucial parameter that guarantee the high overall performance and efficiency of adsorption cooling and water desalination systems. MIL-101(Cr) is a metal-organic framework (MOF) material with a high-water vapour uptake of 1.36–1.47 gH2O gads−1. However, MIL-101(Cr) exhibits an IV isotherm (S- shaped isotherm) which means that the high-water uptake only takes place at high relative pressure (≥0.5). This drawback makes MIL-101(Cr) impractical for adsorption applications working at lower relative pressure such as adsorption cooling and desalination with cooling effect which operate at relative pressures ≤0.4. In this work, MIL-101(Cr)/CaCl2 composites were synthesized, the unsupported and CaCl2 supported materials were fully characterized in terms of their structure (XRD), thermal stability, vibrational spectroscopy structure, morphology (SEM), water adsorption capacity and BET surface area. As a result, incorporating CaCl2 into the MIL-101(Cr) structure significantly enhanced water adsorption characteristics in the desired relative pressure range as the water vapour uptake for Comp_1:8 CaCl2 composite increased from only 0.1 gH2O gads−1 for as-synthesized MIL-101(Cr) to 0.65 gH2O gads−1 at a relative pressure of 0.3.