AnionSelective Redox Electrodes: Electrochemically Mediated Separation with Heterogeneous Organometallic Interfaces

© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 3394 wileyonlinelibrary.com organic synthesis increases the production costs of the compound immensely due to limiting yields of sequential reactions, and thus small improvements in recovery can translate into tremendous economic benefi ts. [ 2 ] Similarly, many renewable energy pathways involve the reduction of stable molecules to form charged anions in the presence of homogeneous catalysts as in, for instance, CO 2 hydrogenation. [ 3 ] In all of these scenarios, the desired organic product is often in a charged state in very dilute amounts (micro to millimolar range) and must be separated from competing ions that are electrolytes, buffers, side-products, catalysts, or co-reagents that are often present in signifi cant excess. From an environmental perspective, organic ions are contaminants of emerging concern to researchers and to the EPA, [ 4,5 ] and present a worldwide problem for both human health and the aquatic ecosystem, in fi rst world and developing countries alike. [ 6 ] A majority of these toxic compounds are anionically charged endocrine-disrupting compounds (EDCs), as well as pharmaceutical and personal care products (PPCPs), [ 5 ] with dangerous concentration levels detected close to agricultural streams and urban drinking water sources. [ 7 ] These compounds include highly toxic pesticides and herbicides [ 4,5 ] such as halocarboxylates and various sulfonate and phosphonate organic compounds, which in the aqueous phase are highly soluble, polar, and charged. [ 8,9 ] Sulfonate groups in particular feature in numerous highly toxic agricultural pesticides, and in environmentally stable surfactant contaminants which accumulate in the ecosystem. [ 9 ] These organic pollutants range from the few millimolar down to nanomolar range in natural aqueous environments, and in the presence of natural hardness and other ions, are extremely challenging to separate selectively by traditional adsorption or fi xed-bed ion-exchange methods. [ 4,5 ]