Conventional carbon capture is limited by high transportation costs and the need for intensive purification. Membrane-based direct air capture is a promising alternative because capture and storage can be performed at the same remote sites, and low CO2 purity is acceptable for geological storage because the impurities are not hazardous. Molecular dynamics simulations of geological storage of CO2-N2-O2 mixtures from direct air capture demonstrated that this approach is both environmentally acceptable and economically viable.