Adsorption isotherms and kinetics of water vapor on novel adsorbents MIL-101(Cr)@GO with super-high capacity

A novel composite (MIL-101@GO) of MIL-101 (Cr) and graphite oxide (GO) with high water vapor capacity for adsorption heat pumps (AHPs) was developed in this work. A series of composites MIL-101@GO with varied GO loading were synthesized using a hydrothermal method, and characterized by N2 adsorption test, SEM, XRD, thermal gravimetric analysis. The adsorption isotherms and kinetics of water vapor over the composites were determined by gravimetric method. Regeneration performance of the composites was evaluated in multiple adsorption-desorption cycles. Results showed that MIL-101@GO possessed a super-high adsorption capacity for water vapor up to 1.58 g/g, which was attributed to its ultrahigh Langmuir specific surface area (5188 m2/g) and pore volume (1.78 cm3/g). The isosteric heat of water vapor adsorption on MIL-101@GO was calculated to be in the range of 44-56 kJ/mol, slightly higher than that on MIL-101 (44-53 kJ/mol). Diffusion coefficients of water vapor over MIL-101@GO composites were ranged from 0.133 × 10−10 to 4.485 × 10−10 cm2/s at 298-313 K. Additionally, six consecutive adsorption-desorption cycles suggesting that the synthesized MIL-101@GO had excellent reversibility and stability for water vapor adsorption. These superior water vapor adsorption/desorption performances make MIL-101@GO a promising candidate as the water vapor adsorbent for AHPs process.