Mixed matrix membranes (MMMs) were prepared by incorporating 10 wt%, 20 wt% and 30 wt% silica gel filler particles into novel ionic cross-linked polyether (IXPE) polymers. Porous silica gel has the advantage of high surface area that can increase the free volume and permeability in a polymer film while also being commercially available and low cost. The MMMs featured high chemical and thermal stability as well as a modest improvement in storage modulus. These features are due to the excellent interfacial interaction between silica gel filler particles and the polymer matrix. Increasing the loading of silica gel particles in MMMs resulted in higher permeability up to 120 Barrer for CO2, which is about 40% higher than the neat polymer matrix. Most importantly, the MMMs maintained a very high CO2/N-2 selectivity performance of around 41 for all particle loadings that were tested.