Effect of introduced g-C3N4 nanosheet interlayers with different morphologies of ZIF-67 on CO2 separation performance

Abstract

The introduction of MOF into the interlayers of two-dimensional (2D) materials has been a promising approach for improving the membranes separation performance. However, how to select MOF 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. Herein, we report a universal strategy to adjust the interlayer distance of the g-C₃N₄ nanosheets by introducing 2D zeolitic imidazolate framework-67 nanosheets (ZIF-67 NS) and 3D bulk-type counterpart (ZIF-67 NB) between g-C₃N₄ layers. The interlayer distances of the g-C₃N₄ nanosheets were precisely regulated from the original 0.325 nm to 0.343 and 0.340 nm after introducing of ZIF-67 NB and ZIF-67 NS, respectively. The increase in linterlayer distances of g-C₃N₄ nanosheet has expanded the interlayer gas transport channels, contributing to the improvement of gas permeability. Notably, compared with ZIF-67 NB, ZIF-67 NS introduced g-C₃N₄ interlayers to prepare ZIF-67 NS@g-C₃N₄/Pebax membrane had superior CO₂ separation selectivity performance with excellent 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. More importantly, the introduction of g-C₃N₄ nanosheets endowed the membrane with excellent separation stability. The study may provide valuable insights for developing novel 2D material membrane with excellent separation performance.