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

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/N-2 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/N-2 adsorption selectivity and CH4/N-2 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. (C) 2014 Elsevier Inc. All rights reserved.