A tough ion gel constructed from an interpenetrating polymer network (IPN) and high ionic liquid (IL) content was developed using a one-pot/one-step method. The IPN structure was composed of the physically cross-linked poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) network and the chemically cross-linked poly(N,N-dimethylacrylamide-co-N-succinimidyl acrylate) (poly(DMAAm-co-NSA)) network, which, respectively, contributed to the high mechanical strength and good IL holding property of the IPN ion gel. The IPN ion gel containing 80 wt % of IL, 10 wt % of PVDF-HFP network, and 10 wt % of poly(DMAAm-co-NSA) network prepared at 50 °C displayed high tensile fracture energy (758 kJ/m3) and a good IL holding property under compression at 1.16 MPa (weight loss of the ion gel: 0.79 wt %). An IPN ion gel membrane with a high IL content of 91.3 wt % was successfully fabricated and showed a high CO2 permeability of 1421 barrer and CO2/N2 permselectivity of 27.