In recent years, growing concern about the effect of anthropogenic CO2 on global climate change have motivated significant interest in renewable energy technologies that are or can be carbon neutral, such as use of wind, solar and biomass-based energy. This is because the atmospheric CO2 concentration has risen about 35% to a value of 390 ppm since the industrial revolution due to widespread use of fossil fuels. Even in the face of significant growth of renewable energy usage, it is expected that the atmospheric CO2 concentration will continue to rise over the next decades. To this end, capture of CO2 from large point sources such as fossil fuel burning power plants has been proposed as a means to reduce anthropogenic CO2 emissions, with the captured CO2 sequestered permanently or semi-permanently geologically, or used to some degree in the synthesis of fuels or chemicals. However, it should be noted that this approach can be at best carbon neutral, and as such, it does not offer the possibility to reduce atmospheric CO2 levels below where they are today. Furthermore, CO2 capture from distributed sources such as cars, planes and ships appears economically unfeasible.
In contrast, CO2 capture from the ambient air can be carbon negative. This concept has been largely overlooked due to the perceived technical difficulty and cost associated with capturing CO2 from extremely diluted sources, where many of the current approaches effective for the point-source capture, such as membrane separation, will not be viable. Process parameters such as CO2 capturing capacity and regeneration energy must be rationally designed to make any process cost-competitive to collect CO2 from such a low concentration source. Adsorptive CO2 fixation shows promise because of its potential to be less energy-intensive, but many of the most common solid sorbents such as zeolites capacities that are not practical for at very low pressures. In this talk, a class of amine-based solid adsorbents is proposed as an effective means for the air capture, allowing for the collection of diluted CO2 from the ambient atmosphere via the chemisorption of CO2 onto the amine functionalities in the hybrids. For example, evaluation of a hyperbranched aminosilica material (HAS) material with a CO2 mixture simulating ambient air (400 ppm) revealed that the CO2 capacity of this adsorbent is only marginally influenced by changing the concentration from 10% to 400 ppm. These results suggest that an air capture process using solid amine-based adsorbents has a potential to be an effective approach for atmospheric CO2 reduction.