Iron catalyst reduces oxyanion pollutants

The extensive use of fertilizers, bleaching agents, propellants, and explosives that contain either nitrate or perchlorate means that these highly soluble and mobile oxyanions often contaminate sources of drinking water—and removing them is tough. Nitrate and perchlorate are known for their weak metal complexation, poor nucleophilicity, and, consequently, their kinetic inertness toward oxidation and reduction. To reduce them, chemists generally resort to harsh reaction conditions, such as low pH, high temperature, and long reaction times. But there are two metalloenzymes—nitrate reductase and perchlorate reductase—that are capable of reducing these oxyanions under mild conditions. Inspired by these enzymes, chemists at the University of Illinois, Urbana-Champaign, led by Alison R. Fout, created an iron-based catalyst (shown) that can reduce nitrate to nitric oxide and perchlorate to chloride (Science 2016, DOI: 10.1126/science.aah6886). The catalyst features a secondary coordination sphere that facilitates deoxygenation of substrates and stabilizes high-valent iron-oxo intermediates. The researchers say the bioinspired iron catalyst is “a first step toward a potentially more sustainable reduction strategy” for oxyanions.