Polyacrylonitrile Nanoparticle-Derived Hierarchical Structure for CO2 Capture

The production of porous clusters by controlled aggregation of polyacrylonitrile nanoparticles and thermal treatment, and their application to CO2 capture are reported. The synthesis of the primary particles by emulsion polymerization exhibits good reproducibility and is easy to scale up. The subsequent gelation of the produced latexes (controlled destabilization by salt addition) results in the formation of macroporous monoliths of nanoparticles with a mean pore diameter of 100 nm. A carefully assessed thermal treatment is applied to the dried monolith after grinding. The produced porous clusters are processed with three high-temperature steps: oxidation, stabilization, and pyrolysis. The latter allows for the creation of micropores in the initially non-porous nanoparticles, thus enabling access to the remaining nitrogen-bearing species present in the pyrolyzed polymer. The relative contributions of the remaining nitrogen-bearing species and of the micropores are elucidated by applying different oxidation temperatures. In particular, the fraction of the pores with diameter smaller than 0.7 nm is decisive in determining the final capture ability. After a treatment including oxidation at 240 °C, stabilization at 350 °C, and pyrolysis at 900 °C, the best reported material shows an average CO2 adsorption capacity of 3.56±0.17 mol (CO2) kg−1 at 0 °C and 1 atm.