Ion-Exchanged ZIF-67 Synthesized by One-Step Method for Enhancement of CO2 Adsorption

Li+- and Na+-exchanged ZIF-67 was synthesized by a new one-step method of ion as-exchange technique and tested as CO2 adsorbents. As a comparison, the standard ion-exchange procedure was also carried out. The powder X-ray diffraction (XRD), scanning electronic microscope (SEM), particle size analyzer (PSD), and thermal gravimetry analysis (TGA) were used to investigate the effect of ion-exchange techniques on the structure of the materials. CO2 uptake of ZIF-67 ion exchanged by one-step method is much higher than that by the standard ion-exchange procedure. All of the adsorption isotherms show linear patterns with stable adsorption rate from 0 bar to 1 bar, which reveals the materials could get excellent adsorption performance at higher pressure range (>1 bar). Elemental analysis, N-2 physical adsorption, and the point of zero charge (PZC) were carried out to confirm the adsorption mechanism. van der Waals interaction determined by the surface area and coordination interaction resulting from electrostatic interaction work in synergy to enhance CO2 adsorption performance of ZIF-67 ion exchanged by the one-step method.