Catalysis Microorganisms have evolved sophisticated enzymatic machinery to reduce perchlorate and nitrate ions. Although the energetics of the pathways are different, the heme-containing active sites of the corresponding reductase enzymes are remarkably similar. Ford et al. constructed an inorganic catalyst to mediate these reactions based on these active sites, using a nonheme iron complex. A secondary coordination sphere near the iron center aligned the nitrate or perchlorate oxyanions and formed an iron-oxo complex. Regenerating the catalyst in the presence of protons and electrons released water—a potentially much more sustainable process than reduction strategies that require the use of harsh reagents. Science , this issue p. [741][1] [1]: /lookup/doi/10.1126/science.aah6886