Nanosilica polyamidoamine dendrimers for enhanced direct air CO capture.

Exploring efficient systems to recover CO from the atmosphere could be a way to address the global carbon emissions issue. Herein, we report the synthesis of nanosilica (NS) functionalized with polyamidoamine (PAMAM) dendrimers (NS-PAMAM) as efficient adsorbents for CO capture under simulated direct air capture (DAC) (400 ppm CO in helium at 30 °C) and indoor air (≥400 ppm, 50 ± 3% RH at 30 °C) conditions. The results inferred that the 1 (NS-G1.0), 2 (NS-G2.0), 3 (NS-G3.0), and 4 (NS-G4.0) generations of the NS-PAMAM dendrimers exhibited excellent performance for CO capture. Compared to the other generations, NS-G3.0 demonstrated superior CO adsorption capacities of 0.50 mmol g under simulated dry CO conditions (400 ppm in He), 1.02 mmol g under indoor air (dry) CO conditions (≥400 ppm, 26 ± 3% RH), and 1.54 mmol g under indoor air (humid) CO conditions (≥400 ppm, 50 ± 3% RH). The study included the evaluation of CO adsorption-desorption performance of the NS-PAMAM dendrimers under varying structural and chemical parameters, kinetics, regeneration at low temperature (80 °C), as well as CO adsorption under humid conditions. Additionally, NS-G3.0 displayed a substantially superior performance with stable CO capture displayed during ten short temperature swing adsorption (TSA) cycles, making it a promising candidate for CO capture from ambient air. Finally, we demonstrated the recovery and reutilization of the captured CO for both the synthesis of formate carbonate hydrogenation and for the production of calcium carbonate pellets.