The establishment of a sustainable CO₂ cycle displays a high-priority target of global climate protection, and energy effciency and environmental care in particular. The envisaged project aims at a molecular understanding of reversible CO₂ uptake from air and subsequent catalytic transformation of CO₂ to sustainable compounds/materials. Such implementation of an energy and resource-effective CO₂ cycle is an ambitious goal. Our approach is based on the recently discovered chemistry of rare-earth-metal coordination compounds with carbon dioxide. The innovative concept takes advantage of the special reactivity of naturally occuring nitrogen compounds toward CO₂. Synergistic effects of metal complexes and porous materials can be anticipated. The working hypothesis is applied to nontoxic light metals with similar properties (and reactivities) as found for the rare-earth metals, ideally minimizing any “energy penalty” as well as “mass penalty”.