Serious and immediate action is needed to reduce carbon emissions and prevent catastrophic global climate change. In this work, we investigate the enhancement of CO2 absorption in water by preparing and adding different types of modified Fe3O4 nanoparticles to a water-base fluid, creating a nanofluid system that has gained increasing interest over the last decade. The nanoabsorbents are prepared by using different inorganic and organic reagents; tetraethyl orthosilicate (TEOS), (3-Aminopropyl) triethoxysilane (APTES) and diethylenetriamine. These coat the as-synthesized, magnetite Fe3O4 core-shell nanoparticles resulting in a symmetric, amine-based nanodendritic CO2 adsorbent. These reagents were chosen due to their range of various functional groups and hydrophobic or hydrophilic nature, as well as to assess their effect on the absorption of CO2. In addition to evaluating the prepared nanofluidic system (nanoparticle/water nanofluids), we also studied the effects of nanoparticle loading, hydrophilicity, the quantity of nanoparticles, reaction temperature, and absorption time on the CO2 absorption. The nanodendritic absorbent, with a high density of symmetric amine functional sites and hydrophilicity (Fe3O4@SiO2-SNH2), showed the highest enhancement of CO2 absorption (70%) in comparison to the water-based solution, which is higher than that of most reported nanofluidic systems. Fe3O4@SiO2-SNH2 also retains its performance even after being regenerated for 5 absorption cycles, losing only 3% of its absorption efficiency over this period. Finally, the significant CO2 absorption, high recyclability under low temperature, and mild regeneration in a water-based nanofluid, as a "green" solvent, make this nanofluidic system a unique candidate for atmospheric CO2 capture.