Recyclable nanocomposites for carbon dioxide fixation and membrane separation using waste polycarbonate

In this study, polymer nanocomposite membranes with recyclability were developed to achieve good mechanical properties and gas permeability in the consumption of a recycled polymeric material. The newly developed process has been realized through the conversion of waste PC to afford key intermediates containing alkoxysilane and phenolic groups. The alkoxysilanes would act as the nucleation sites for sol–gel reactions, whereas the phenolic groups further provided active hydrogens for click reactions in the production of polyurethane/silica (PU/SiO2) nanohybrids, exhibiting microcavity to facilitate gas molecules diffusion for membrane with improved gas permeability. Moreover, the additional use of aliphatic polycarbonate polyol provided enhanced CO2 solubility for gas separation membranes of the PU/SiO2 nanohybrids with a PCO2 permeability of 24.02 barrer and a selectivity of 32.85 (αCO2/N2), which approached the 2008 Robeson upper bounds. Moreover, the joint presence of polycarbonate polyol and silica in the nanohybrids led to high-performance elastomeric properties, with tensile strengths of 35.5 MPa and over 700 % elongation at break, results that exceeded those of previously reported PU-based gas separation membranes. Notably, this PC recycling process featured the newly formed carbamate groups as the reaction sites, enabling the recyclability of PU/SiO2 nanohybrids as the gas separation membranes for CO2 capture and storage in post-consumption materials.