Drinking water contamination
with heavy metals, particularly lead,
is a persistent problem worldwide with grave public health consequences.
Existing purification methods often cannot address this problem quickly
and economically. Here we report a cheap, water stable metal–organic
framework/polymer composite, Fe-BTC/PDA, that exhibits rapid, selective
removal of large quantities of heavy metals, such as Pb2+ and Hg2+, from real world water samples. In this work,
Fe-BTC is treated with dopamine, which undergoes a spontaneous polymerization
to polydopamine (PDA) within its pores via the Fe3+ open
metal sites. The PDA, pinned on the internal MOF surface, gains extrinsic
porosity, resulting in a composite that binds up to 1634 mg of Hg2+ and 394 mg of Pb2+ per gram of composite and
removes more than 99.8% of these ions from a 1 ppm solution, yielding
drinkable levels in seconds. Further, the composite properties are
well-maintained in river and seawater samples spiked with only trace
amounts of lead, illustrating unprecedented selectivity. Remarkably,
no significant uptake of competing metal ions is observed even when
interferents, such as Na+, are present at concentrations
up to 14 000 times that of Pb2+. The material is
further shown to be resistant to fouling when tested in high concentrations
of common organic interferents, like humic acid, and is fully regenerable
over many cycles.