Carbon dioxide basic water illustrates this property, in which case hydroxide is the nucleophile. Other nucleophiles react as well. For example, carbanions as provided by Grignard reagents and organolithium compounds react with to give carboxylates: In metal carbon dioxide complexes, serves as a ligand, which can facilitate the conversion of to other chemicals. The reduction of to CO is ordinarily a difficult and slow reaction: Photoautotrophs (i.e. plants and cyanobacteria) use the energy contained in sunlight to photosynthesize simple sugars from absorbed from the air and water: The redox potential for this reaction near pH 7 is about −0.53 V "versus" the
Carbon dioxide removal targets and . In the "OECD Environmental Outlook to 2050" released at the 2011 United Nations Climate Change Conference, the authors commented on the need for negative emissions, stating "Achieving lower concentration targets (450 ppm) depends significantly on the use of BECCS". A carbon dioxide sink such as a concentrated group of plants or any other primary producer that binds carbon dioxide into biomass, such as within forests and kelp beds, is not carbon negative, as sinks are not permanent. A carbon dioxide sink of this type moves carbon, in the form of carbon dioxide, from the atmosphere or hydrosphere