Evaluation of piperazine/MIL-101 sorbents for enhanced low-temperature CO2 removal

In the present work, the metal-organic framework MIL-101(Cr) was modified by grafting with piperazine (Pz) in order to enhance the low-temperature CO₂ adsorption characteristics. The effect of piperazine loading was studied by varying the percentage of piperazine (0%, 20%, 50%, and 80%). The adsorbent materials were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), N₂ adsorption-desorption, and thermogravimetric analysis (TGA). The characterization studies confirmed the successful incorporation of piperazine on MIL-101. The CO₂ adsorption kinetics and adsorption isotherms model were investigated at three different temperatures (30 °C, 40 °C, and 50 °C) to better understand the behavior of CO₂ adsorption on the synthesized adsorbents. It was found that 50%pz/MIL-101 can enhance CO₂ capacity up to 67% compared to bare MIL-101. Furthermore, piperazine grafted on MIL-101 can increase the rate constant and improve the binding energy between CO₂ molecules and the surface of adsorbents. The regenerability for CO₂ adsorption of pz/MIL-101 had nearly no drop after eight adsorption-desorption cycles. Thus, the pz/MIL-101 provides an excellent opportunity to capture CO₂ in industrial applications.