Carbon dioxide (CO2) is an atmospheric greenhouse gas that feeds all life, plays a critical role in global warming, and could constitute an inexpensive carbon source for future sustainable industries. While synthetic chemistry lacks suitable catalysts to functionalize carbon dioxide in mild reaction conditions, autotrophs do it constantly, and thus there is increasing interest in exploiting the CO2-fixation mechanisms offered by nature. In this exchange proposal, we propose fast time-resolved structural-dynamics studies of one of the fastest CO2-fixation enzymes, enoyl-CoA carboxylase/reductase (ECR), using ambient temperature serial X-ray crystallography on Beamline ID29, ESRF, which achieves 10μs resolution. This study will reveal details of the enzyme subunit coupling as well as the enzyme-substrate interactions to correlate the structural and functional states of the enzyme during fixation and pave the way for faster biomolecule productions using engineered C-cycling enzymes.