Highly Enhanced Selectivity and Easy Regeneration for the Separation of CO2 over N2 on Melamine-Based Microporous Organic Polymers

Abstract

Melamine based microporous organic polymers (MBMOPs) have been prepared via a one-pot polymerization using the Schiff base reaction. Various techniques such as FT-IR, Ar adsorption, SEM, TEM, and TG have been used to characterize the textural structure, porosity, and stability of the synthesized MBMOPs. The adsorption isotherms of CO2 and N2 on MBMOPs have been accurately measured at pressures up to 118 kPa and different temperatures. Ascribed to the specific affinity of amine groups for CO2, the robust microporous MBMOPs display excellent CO2 adsorption performance in terms of both capacity, up to 2.8 mmol g–1 at 273 K and 118 kPa, and selectivity over N2. Dual-site Langmuir (DSL) or single-site Langmuir (SSL) model describes well the equilibrium data for the adsorption of CO2 or N2 on MBMOPs, respectively. The binary gas adsorption isotherms predicted by the ideal adsorbed solution theory (IAST) show that the prepared MBMOPs exhibit very high selectivities for CO2 over N2, up to 83.7, for equimolar mixtures of CO2 and N2 at 298 K and 100 kPa. The dynamic CO2 adsorption capacity and selectivity against N2 over MBMOPs have been experimentally investigated by breakthrough column technique at 1 bar and 298 K, indicating that a complete separation is available. Remarkably, CO2 capture–regeneration experiments indicate that MBMOPs can be easily regenerated by only purging with He or N2 rather than by raising the temperature, suggesting that MBMOPs are promising candidates of pressure swing adsorption (PSA) adsorbents for the separation of CO2–N2.