Cr-doped UiO-66 with enhanced water adsorption for adsorption heat transformation

Abstract

In this study, the possible applications of Cr-doped UiO-66 in adsorption heat transformation (AHT) were investigated. Four different Cr-doped UiO-66 samples were prepared to examine their structures and water adsorption properties. Results showed that Cr-doped UiO-66 samples have higher pore volume and specific surface area than pure UiO-66 samples. In particular, 0.2Cr-UiO-66 has the highest BET specific surface area (993 m 2 /g) and micropore volume (0.50 cm 3 /g), which are 31.6% and 29.6% higher than those of unmodified UiO-66, respectively. Water adsorption tests revealed that Cr doping can improve the water adsorption performances of UiO-66. At 25 °C and P/P 0 = 0.9, the saturated water uptake of 1.0Cr-UiO-66 is 0.69 g/g, which is 64.3% higher than that of pure UiO-66. After 10 adsorption/desorption cycles, the water adsorption capacity of pure UiO-66 and 0.5Cr-UiO-66 samples has decreased by 3.4% and 5.7%, respectively, indicating their good cycle stability. All these results indicate that Cr doping is beneficial to UiO-66 application in AHT. • Metal-organic framework UiO-66 were modified with Cr by solvothermal method. • Cr-doped UiO-66 showed enhanced saturated water adsorption capacity and water uptake at low water pressure. • The BET specific surface area of UiO-66 was increased by 31.5% with the addition of Cr. • Water adsorption capacity of 0.5Cr-UiO-66 remains most constant after cycling.