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

• Robust PU/SiO 2 nanohybrids with a tensile strength of 35.5 MPa and over 700 % elongation at break. • Nanohybrids prepared from polymer waste conversion process with an approximately 98% functional group selectivity. • Nanohybrids exhibiting particle sizes ranging from 100 to 500 nm. • PU/SiO 2 membrane involving CO 2 reuse with a P CO2 of 24.02 barrer, and a selectivity of 32.85 ( α CO2/N2 ). • Gas separation membranes for CO 2 capture and storage from post-consumption materials. 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/SiO 2 ) nanohybrids, exhibiting microcavity to facilitate gas molecules diffusion for membrane with improved gas permeability. Moreover, the additional use of aliphatic polycarbonate polyol provided enhanced CO 2 solubility for gas separation membranes of the PU/SiO 2 nanohybrids with a P CO2 permeability of 24.02 barrer and a selectivity of 32.85 ( α CO2/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/SiO 2 nanohybrids as the gas separation membranes for CO 2 capture and storage in post-consumption materials.