A single-stage 4-step pressure-vacuum swing adsorption (PVSA) process, capable of CO2 separation from the prepared flue gas, is experimentally studied on a fresh perspective of energy-efficiency analysis. The major contribution of thermodynamic carbon pump, which includes the minimum CO2 separation work and the second-law efficiency, is to establish the relationship between energy consumption and separation difficulty. Adsorption/desorption cycles utilizing a fixed bed of an adsorbent material made of zeolite 13X are performed. Not only the recovery target, but also the second-law efficiency is considered as the main performance criteria in this paper. Thereby, the performance analysis of experimental apparatus is conducted over a range of process parameters, namely 10-20% CO2 concentration, 1.0-3.0 sl/min flow rate, 10-30 s time duration of pressurization with feed, 80-120 s time duration of feed and 40-80 s time duration of purge. The results show that the specific energy consumption for the 4-step PVSA experiments is varied from 2719.31 kJ/kg to 9334.21 kJ/kg, the corresponding range of second-law efficiency calculated by thermodynamic carbon pump is 1.83-4.27%. The efficiency of vacuum pump affects the specific energy consumption of CO2 capture process. The second-law efficiency in experimental studies of this paper is strongly dependent on the mechanical work performance of vacuum pump.