Effect of Introduced G-C3n4 Nanosheet Interlayers with Different Morphologies of Zif-67 on Co2 Separation Performance

Abstract

The introduction of nanoparticles into the interlayers of two-dimensional (2D) membranes has appeared recently. However, how to selectively particles with different morphologies to be introduced into the 2D membrane interlayers to precisely control the interlayer distance to enhance the CO2 separation performance is still a challenge. Here, we report a universal strategy to adjust the interlayer distance of the nanosheets by introducing 2D zeolitic imidazolate framework-67 nanosheets (ZIF-67 NS) and 3D bulk-type counterpart (ZIF-67 NB) between g-C3N4 layers. Additionally, the introduction of different morphologies of ZIF-67 increased the interlayer distance of the nanosheets, which further extended the interlayer gas transport channels and was beneficial to improving the gas permeability. XRD results showed that the interlayer distances of g-C3N4 layers increased from the original 0.325 nm to 0.343 and 0.340 nm after the interlayer introduction of ZIF-67 NB and ZIF-67 NS, respectively. Compared with ZIF-67 NB, ZIF-67 NS introduced g-C3N4 interlayers to prepare ZIF-67 NS@g-C3N4/Pebax membrane with higher CO2 separation selectivity. When the concentration of ZIF-67 NS reaches 0.75 mg mL-1, the ZIF-67 NS-3@g-C3N4/Pebax membrane exhibits a maximum CO2 permeability of 1001.96 Barrer and CO2/N2 selectivity of 51.65, and CO2/CH4 selectivity of 55.78 at 25 °C and 1 bar. Notably, the membrane was tested for its excellent separation stability after 100 h of long-term operation, indicating significant potential for industrial applications.

Keywords: CO2 Separation, g-C3N4 nanosheets, ZIF-67 NB, ZIF-67 NS