Molar-scale formate production via enzymatic hydration of industrial off-gases

Decarbonizing the steel industry, a major CO2 emitter, is crucial for achieving carbon neutrality. Escaping the grip of CO combustion methods, a key contributor to CO2 discharge, is a seemingly simple yet formidable challenge on the path to industry-wide net-zero carbon emissions. Here we suggest enzymatic CO hydration (enCOH) inspired by the biological Wood‒Ljungdahl pathway, enabling efficient CO2 fixation. By employing the highly efficient, inhibitor-robust CO dehydrogenase (ChCODH2) and formate dehydrogenase (MeFDH1), we achieved spontaneous enCOH to convert industrial off-gases into formate with 100% selectivity. This process operates seamlessly under mild conditions (room temperature, neutral pH), regardless of the CO/CO2 ratio. Notably, the direct utilization of flue gas without pretreatment yielded various formate salts, including ammonium formate, at concentrations nearing two molar. Operating a 10-liter-scale immobilized enzyme reactor feeding live off-gas at a steel mill resulted in the production of high-purity formate powder after facile purification, thus demonstrating the potential for decarbonizing the steel industry. With the global climate crisis, approaches to capture emissions are critical, with the heavy industry sector being particularly challenging to decarbonize. The authors describe a new enzyme cascade for converting industrial emissions into formate salts as a hydrogen carrier or building block for chemicals.