The present invention discloses a membrane-less reactor design for microbial electrosynthesis of alcohols from carbon dioxide (CO2). The membrane-less reactor design thus facilitates higher and efficient CO2 transformation to alcohols via single pot microbial electrosynthesis. The reactor design operates efficiently avoiding oxygen contact at working electrode without using membrane, in turn there is an increase in CO2 solubility and its bioavailability for subsequent CO2 conversion to alcohols at faster rate. The present invention further provides a process of operation of the reactor for biotransformation of the carbon dioxide.