Bioactive nanofluids for enhancing carbon dioxide capture

• The biocatalyst significantly enhanced CO 2 absorption in nanofluids. • GO outperformed other nanoparticles, improving CO 2 capture by up to 42%. • Improved stability and reusability was achieved by carbonic anhydrase immobilization. • GO-CA nanobiocatalyst retains 87% activity after multiple CO 2 capture cycles . The pressing need to reduce industrial CO₂ emissions has spurred the development of efficient and sustainable alternatives to conventional amine-based solvents. In this study, a series of novel nanobiocatalysts were engineered by immobilizing carbonic anhydrase (CA) onto four types of CO₂-affinitive nanoparticles: zeolitic imidazolate framework-8 (ZIF-8), Fe₂O₃, graphene, and graphene oxide (GO). The resulting nanobiocatalysts exhibited enhanced CO₂ adsorption capacities, with GO achieving the highest at 22.4 mg/g, followed by ZIF-8 at 8.6 mg/g at 25 °C. When used as nanofluids, all systems significantly outperformed pure water in CO₂ absorption, with GO reaching a maximum CO₂ flux of 225 mol/m²·min at 1 bar and 25 °C. The presence of immobilized CA contributed to substantial flux enhancements: 41.6% for GO, 36.9% for graphene, 32.0% for ZIF-8, and 21.0% for Fe₂O₃, demonstrating a clear synergistic effect between enzymatic catalysis and nanoparticle-assisted absorption. The GO-CA nanobiocatalyst also exhibited excellent operational stability, retaining over 95% of its initial performance after three reuse cycles. Post-reaction analysis revealed a decrease in GO’s surface area from 1562 m²/g to 338 m²/g, confirming stable enzyme immobilization. These results underscore the potential of GO-CA nanobiocatalysts as a high-performance, reusable, and scalable solution for industrial CO₂ capture. .