Many inorganic pollutants in the form of metal oxo-hydroxo anions are listed as EPA (U.S. Environmental Protection Agency) priority pollutants. Recently, EPA set a national limit for perchlorate (ClO 4 ร , a widespread anion occurring from rocket fuel, fireworks and other sources) in drinking water. Chromate (CrO 4 2ร ) and pertechnetate (TcO 4
ร
) are also problematic monomeric oxo anions, in this case upon the vitrification of radioactive waste. Meanwhile, pharmaceuticals and their metabolites have gained increasing attention as pollutants, many existing as organic anions at neutral pH. Current treatment processes are insufficient to adsorb them in high capacity and at reasonable cost. Chlorination can lead to even more toxic compounds, such as monohalogenated or oxidized by-products. The typical approach to trap these intrinsically anionic pollutants remains ion exchange resins, though these organic polymers possess limited thermal and chemical stability and thus longevity. Cationic inorganic layered materials are 2-D extended architectures where the positively charged layers are held together electrostatically by charge-balancing anions. One typical and widely studied example is the layered double hydroxides (LDHs) with general formula
where M 2+ and M 3+ are a range of metals (e.g. Mg 2+ and Al 3+ ), x is the ratio of M 3+ /(M 2+ +M 3+ ), and A nร are n-valent interlamellar anions (e.g.