Hold on tight! Reaction of CO2 with unsaturated alcohols and tBuOI to form cyclic carbonates leads to fixation of the greenhouse gas. In contrast to known CO2 fixation methods, this process proceeds under extremely mild conditions. Detailed facts of importance to specialist readers are published as "Supporting Information". Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.