(537a) Direct Air Capture over Porous Transition Mixed Metal Oxides

Low-costs direct air capture (DAC) technologies are urgently needed to mitigate CO₂ emissions and avert adverse effects of climate change. Solid sorbent-based technologies have shown promise for DAC applications, but high sorbent costs for traditional capture materials such as supported amines and metal-organic frameworks that represent a large fraction of the overall DAC cost limit its widespread use. Inexpensive metal oxides such as MgO and CaO have been explored as potential DAC solid sorbents, but require high regeneration temperatures and exhibit slow adsorption kinetics. We show herein that porous transition metal oxides (PTMOs) can capture CO₂ from simulated air at ambient temperatures. The PTMO materials exhibit promising DAC capacities that increase under humid environments (Figure 1). The CO₂ adsorption capacity of these materials can be tuned through aliovalent doping (Figure 1), with optimal adsorption capacities achieved at intermediate dopant loadings. In-situ FTIR data suggest the formation of multiple carbonate species on PTMOs during DAC. Moreover, the material can be subjected to several temperature swing adsorption cycles. Overall, our findings reveal that PTMOs can serve as a new class of solid DAC sorbents that are significantly less expensive and more tunable compared to existing classes of sorbents.