Predictions of future climate change have triggered a search for ways to reduce the release of greenhouse gases into the atmosphere. Carbon capture and storage (CCS) assists this goal by reducing carbon dioxide emissions, and CO₂ adsorbents in particular can reduce the costs of CO₂ capture. Here, we review the nanoscale sorbent materials that have been developed and the theoretical basis for their function in CO₂ separation, particularly from N₂-rich flue gases.