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

Abstract

Abstract Decarbonizing the steel industry, a major CO2 emitter, is crucial for achieving carbon neutrality1,2. Escaping the grip of CO combustion methods, a key contributor to CO2 discharge is a seemingly simple yet formidable challenge on the path to industrial-wide net-zero carbon emissions1,3–5. Here we suggest the 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 varying CO/CO2 ratios. Notably, the direct utilization of flue gas without pretreatment yielded various formate salts, including ammonium formate, at concentrations nearing two molars. Operating the 10 L-scale immobilized enzyme reactor at the steel mill resulted in the production of high-purity formate powder after facile purification, thus demonstrating the potential for decarbonizing the steel industry.