Bicarbonate-mediated proton transfer requires cations

Near-neutral HCO 3 – aqueous solution plays an essential role in respiratory, mineralization and catalysis, yet the interconversion between hydrated CO 2 , HCO 3 – and CO 3 2– and the associated proton transfer under such proton-deficient conditions remain uncovered. Here we reveal that cation enables HCO 3 – to self-dissociate into OH – and CO 2 through a pH-independent process, where CO 2 hydration and subsequent proton transfer in acid-base reactions lead to the overall exchange of oxygen isotopes between HCO 3 – and H 2 O tracked by oxygen isotope-labeled Raman spectroscopy. Isolating HCO 3 – from cations with crown ether impedes HCO 3 – dissociation and the following reactions. Further molecular dynamics simulations demonstrate that the interplay between HCO 3 – and hydrated cations drives HCO 3 – dissociation. This study suggests a natural proton channel upon coupling HCO 3 – with cations.