Separation of CO2/CH4 and CH4/N2 mixtures by M/DOBDC: A detailed dynamic comparison with MIL-100(Cr) and activated carbon

•M/DOBDC (Mg, Co and Ni) were studied on separation of CO2/CH4 and CH4/N2 mixtures.•Adsorption equilibrium times were investigated in the adsorption process.•Mg/DOBDC appears to be the best candidate for CO2/CH4 separations.•Ni/DOBDC separated CH4/N2 more efficiently with high CH4/N2 adsorption ratio.

In this report we studied the gas adsorption and breakthrough characteristics of M/DOBDC (M = Mg, Co, or Ni) metal–organic frameworks, with honeycomb-like structures and high concentrations of coordinatively unsaturated sites. We studied these characteristics by using M/DOBDC to separate CO2/CH4 and CH4/N2 mixtures and compared those results to separation using MIL-100(Cr) and activated carbon, particularly focusing on the adsorption capacities and equilibrium times. We show that the presence of coordinatively unsaturated sites greatly influences gas adsorption, separation, and regeneration. Mg/DOBDC displayed excellent separation efficiency for CO2/CH4 and simple regeneration under dynamic conditions, while Ni/DOBDC had superior CH4/N2 adsorption selectivity and CH4/N2 separation and exhibited strong interactions between CH4 molecules and its coordinatively unsaturated Ni atoms. Overall, the M/DOBDC frameworks demonstrated extremely high capacity, high selectivity, and easy regeneration for CO2 and CH4 separation under dynamic conditions, making them suitable for gas separation.

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