Sustainable Carbon Dots from Olive Pomace: Boosting CO ₂ Separation in Mixed Matrix Iongel Membranes

Carbon dioxide (CO2) separation remains a critical challenge in mitigating industrial emissions, driving the development of innovative membrane technologies to improve separation performance. In this study, carbon dots (CDs) obtained from wet olive pomace were incorporated into mixed matrix iongel membranes (MMIMs) by UV-initiated free radical polymerization of poly(ethylene glycol) diacrylate (PEGDA) in the presence of the [C2mim][TFSI] ionic liquid. Dense and defect-free MMIMs with suitable thermal stability were successfully prepared, achieving a homogeneous dispersion of CDs within the iongel matrix at loadings of up to 1 wt %. Gas permeation experiments revealed a significant enhancement in the CO2 permeability and ideal selectivity upon the incorporation of CDs. The MMIM containing 0.5 wt % CDs exhibited the best performance, achieving a CO2 permeability of 725 Barrer, along with CO2/N2 and CO2/CH4 selectivities of 40 and 22, respectively. This outstanding performance surpasses that of previously reported MMIMs and approaches the upper bounds of CO2/N2 and CO2/CH4. Furthermore, the use of biomass-derived CDs as fillers not only improves the CO2 separation performance of MMIMs, but also promotes the sustainable valorization of agricultural waste, offering both environmental and functional advantages.