Bicarbonate-mediated proton transfer requires cations

Abstract

Abstract Near-neutral HCO3 – aqueous solution plays an essential role in respiratory, mineralization and catalysis, yet the interconversion between hydrated CO2, HCO3 – and CO3 2– and the associated proton transfer under such proton-deficient conditions remain uncovered. Here we reveal that cation enables HCO3 – to self-dissociate into OH– and CO2 through a pH-independent process, where CO2 hydration and subsequent proton transfer in acid-base reactions lead to the overall exchange of oxygen isotopes between HCO3 – and H2O tracked by oxygen isotope-labeled Raman spectroscopy. Isolating HCO3 – from cations with crown ether impedes HCO3 – dissociation and the following reactions. Further molecular dynamics simulations demonstrate that the interplay between HCO3 – and hydrated cations drives HCO3 – dissociation. This study suggests a natural proton channel upon coupling HCO3 – with cations.