Modifying polymeric membranes using nanofiller is a promising method to enhance gas permeability and selectivity performance. This work used two types of ZIF-8 functionalized-2D nanofillers to fabricate polyethersulfone mixed matrix membranes. The rGO/ZIF-8 and MoS2/ZIF-8 nanofillers were first synthesised and characterised using FTIR and XRD. Then, 10 wt% of each nanofillers was added to the PES solution. TGA analysis indicates that MMMs containing rGO/ZIF-8 and MoS2 /ZIF-8 exhibit improved thermal stability. No additional peaks in FTIR and XRD were observed in the MMMs, indicating that the 2D nanofillers were compatible with the PES matrix. The MMMs show significantly enhanced gas separation properties where the highest selectivity was observed for 10 wt%PRG/Pebax membrane of 35.71 with CO2 permeability of 611 barrer and CH4 permeability of 17.11 barrer. These results confirm the possibility of using 2D nanofillers to develop high-performance membranes for gas separation.