The potential of hydroquinone (HQ) clathrates to selectively separate/capture CO2 from mixtures of CO2 and H-2 gas is investigated. Selective CO2 enclathration within cages of a HQ framework, from mixtures of various concentrations of the two gases, are identified using C-13 nuclear magnetic resonance (NMR) and Raman spectra. Spectroscopic results indicate that CO2 molecules from the gas mixture are exclusively accommodated into the cages of HQ clathrates and that the H-2 molecules are thereby concentrated in the remaining gas phase. Quantitative evidence is presented by deconvolution of NMR peaks and an elemental analyzer that CO2 molecules can be captured into the clathrate compound even at the partial CO2 fugacity of 0.38 MPa in the gas mixtures tested. Storage capacity of 53-64.4 L of CO2/kg of HQ for the HQ clathrate with full conversion makes a HQ-clathrate-based process viable for pre-combustion CO2 separation.