Herein, for the first time, mesoporous dendritic fibrous nanosilica (DFNS) is utilized to fabricate mixed matrix membranes (MMMs) to increase the membrane properties and push gas separation performance of low-molecular-weight polyethylene glycol (PEG) impregnated MMMs toward superior CO2 capture. The basic physicochemical and gas transport properties of various membranes have been examined in detail for clarifying the mechanism of the significant enhancement in membrane performance. The polymer chains around the DFNS became rigidly according to the enhanced T-g of the MMMs, gas permeability of the gas improved mainly ascribe to the increase of gas diffusivity. Because of the high porosity of DFNS with the mainly specific pore size range of 2-4 nm, the incorporation of novel mesoporous DFNS in cross-linked CO2-philic poly (ethylene oxide) (PEO) matrix can not only promote gas transportation, but also increase the loading rate of low-molecular-weight PEG in membranes. Meanwhile, the introduction of PEGDEM-500 into the DFNS reduces the influence of non-selective interface on the selectivity. We identified the optimized performance of low-molecular-weight PEG impregnated PEO-based MMMs demonstrates the superior CO2 permeability (up to 2281.1 Barrer, a 478.5% increment than that of original UV cross-linked PEO membrane) and high selectivity (up to 48.1 for CO2/N-2), which can easily surpass the (2008) Robeson's Upper Bound. The long-term stability of our membrane is also excellent, which makes great promise for CO2 capture in CCS towards sustainably environmental remediation.