Synthesis of Size-Tunable CO₂-Philic Imprinted Polymeric Particles (MIPs) for Low-Pressure CO₂ Capture Using Oil-in-Oil Suspension Polymerization

Highly selective molecularly imprinted poly[acrylamide-co-(ethylene glycol dimethacrylate)] polymer particles (MIPs) for CO₂ capture were synthesized by suspension polymerization via oil-in-oil emulsion. Creation of CO₂-philic, amide-decorated cavities in the polymer matrix led to a high affinity to CO₂. At 0.15 bar CO₂ partial pressure, the CO₂/N₂ selectivity was 49 (corresponding to 91% purity of the gas stream after regeneration), and reached 97 at ultralow CO₂ partial pressures. The imprinted polymers showed considerably higher CO₂ uptakes compared to their nonimprinted counterparts, and the maximum equilibrium CO₂ capture capacity of 1.1 mmol g^-1 was achieved at 273 K. The heat of adsorption was below 32 kJ mol^-1 and the temperature of onset of intense thermal degradation was 351-376 °C. An increase in monomer-to-cross-linker molar ratio in the dispersed phase up to 1:2.5 led to a higher affinity toward CO₂ due to higher density of selective amide groups in the polymer network. MIPs are a promising option for industrial packed and fluidized bed CO₂ capture systems due to large particles with a diameter up to 1200 μm and irregular oblong shapes formed due to arrested coalescence during polymerization, occurring as a result of internal elasticity of the partially polymerized semisolid drops.