Transition Metal-Free CO₂ Fixation into New Carbon-Carbon Bonds

CO₂ is the ultimate renewable carbon source on Earth and the essential C₁ building block for carbohydrate biosynthesis in photosynthetic organisms. Modern synthetic chemistry is facing the key challenge of developing fundamental transformations, such as C-C bond formation, in a sustainable and efficient manner from renewable sources. In this Minireview, the most significant methods recently reported for CO₂ fixation under transition metal-free conditions are summarized, organized into three different chapters according to the nature of the chemical transformation that forges the new C-C bond. The focus is on the mechanistic aspects of the different CO₂ activation modes, with specific attention to those systems that operate under catalytic conditions.