The research quest in carbon dioxide (CO2) separation technology through the polymeric membrane is intensive at this time of energy and environmental crisis. But, the pursuit of membranes with high selectivity and flux without trading it off for stability, still exists as a challenge. We report a novel membrane prepared by rational blending of two biopolymers: chitosan (CS) that acts as a matrix and silk fibroin (SF) that aids chitosan as a carrier for facilitated transport. The separation of binary gas mixture (CO2/N-2) has been studied at temperature, feed absolute pressure and sweep water flow rate ranging from 60 to 120 degrees C, 2 to 5.93 bar and 0.01 to 0.07 ml/min, respectively. The optimum CO2 permeance of 140 GPU and CO2/N-2 selectivity of 103 for binary gas were observed at 90 degrees C and 0.05 ml/min of sweep water flow rate for the membrane containing 45 wt% of SF in blend with CS (SF45). The SF45 composite membrane exhibited CO2 permeance of 123 GPU and selectivity of 93 and 60 for CO2/N-2 and CO2/H-2 respectively, in case of ternary gas mixtures (CO2/N-2/H-2) at the similar operating conditions. The appreciable CO2 separation performance tunable with temperature and moisture, displayed unprecedented stability for 30 days.