In this study, we investigated semiclathrate-based CO2 capture from the simulated flue gas mixture of fossil fuel-fired power plants in the presence of tetra-n-butyl ammonium chloride (TBAC), primarily focusing on thermodynamic, kinetic, and spectroscopic aspects. The semiclathrate phase equilibria of the quaternary CO2 (20%) + N-2 (80%) + TBAC (1.0, 3.3, and 5.0 mol%) + water mixtures showed that TBAC solutions form semiclathrates with guest gases at significantly stabilized pressure and temperature conditions. CO2 was found to be selectively captured and thus enriched to approximately 60% in the semiclathrate phase. CO2 selectivity in the semiclathrate phase was independent of TBAC concentrations, even though the 3.3 mol% TBAC solution yielded a higher gas uptake and a larger CO2 concentration change in the vapor phase during TBAC semiclathrate formation than the 1.0 mol% TBAC solution. In addition, Raman spectroscopic results demonstrated that both CO2 and N-2 are captured in the TBAC semiclathrate lattices and that there is no structural transition due to the enclathration of guest gases. The overall experimental results are very informative in understanding selective partitioning of flue gas mixtures and guest distributions in the TBAC semiclathrates, may thus be useful in the development of the CO2 capture process using semiclathrates. (C) 2015 Elsevier B.V. All rights reserved.