[en] Highlights: • Hydroquinone (HQ) and a CO₂/CH₄ gas mixture can form a mixed gas HQ clathrate. • The use of HQ gas clathrates appears as a promising alternative avenue of research for innovative applications. • Phase equilibrium data on mixed-gas HQ clathrate are presented for the first time. • Clathrate selectivity is studied and preferential capture of CH₄ molecules is obtained at equilibrium conditions. • Good agreement is obtained between the experimental data and model prediction. - Abstract: Hydroquinone (HQ) clathrates seem to be promising inclusion compounds for selective CO₂ capture from gas mixtures. However, to date no phase equilibrium data are known in literature for mixed-gas HQ clathrates. This study presents experimental equilibrium pressures obtained within a range of 298–343 K for different CO₂/CH₄ gas mixtures. The clathrate composition is given for each equilibrium point. The capture selectivity is calculated from the molar composition of the CO₂/CH₄ gas mixture in the clathrate and in the gas phase. The results obtained reveal that CH₄ molecules in the CO₂/CH₄ mixtures are preferentially captured at equilibrium conditions. Our experimental data are compared against numerical predictions obtained from thermodynamic modeling using the Conde’s model. Very good agreement is found between the calculated and experimental data in terms of clathrate phase equilibria.