The energy penalty corresponds to the amount of energy required to capture a unit of CO2, whereas productivity specifies how much CO2 a unit of the adsorption bed (e.g., a kg or m 3 ) can capture per unit of time. These KPIs are related to the operating and capital costs of the separation, and have been widely adopted in previous screening studies as the indicative metrics of material performance. Mathematical definitions for each KPI are provided in supplementary note 2.