Production of spherical mesoporous molecularly imprinted polymer particles containing tunable amine decorated nanocavities with CO₂ molecule recognition properties

Novel spherical molecularly imprinted polymer (MIP) particles containing amide-decorated nanocavities with CO₂ recognition properties in the poly[acrylamide-co-(ethyleneglycol dimethacrylate)] mesoporous matrix were synthesized by suspension polymerization using oxalic acid and acetonitrile/toluene as dummy template and porogen mixture, respectively. The particles had a maximum BET surface area, S_BET, of 457 m²/g and a total mesopore volume of 0.92 cm³/g created by phase separation between the copolymer and porogenic solvents. The total volume of the micropores (d < 2 nm) was 0.1 cm³/g with two sharp peaks at 0.84 and 0.85 nm that have not been detected in non-imprinted polymer material. The degradation temperature at 5% weight loss was 240–255 °C and the maximum equilibrium CO₂ adsorption capacity was 0.56 and 0.62 mmol/g at 40 and 25 °C, respectively, and 0.15 bar CO₂ partial pressure. The CO₂ adsorption capacity was mainly affected by the density of CO₂-philic NH₂ groups in the polymer network and the number of nanocavities. Increasing the content of low-polar solvent (toluene) in the organic phase prior to polymerization led to higher CO₂ capture capacity due to stronger hydrogen bonds between the template and the monomer during complex formation. Under the same conditions, molecularly imprinted particles showed much higher CO₂ capture capacity compared to their non-imprinted counterparts. The volume median diameter (73–211 μm) and density (1.3 g/cm³) of the produced particles were within the range suitable for CO₂ capture in fixed and fluidized bed systems.