Convenient Detection of Pd(II) by a Metal–Organic Framework with Sulfur and Olefin Functions

A highly specific, distinct color
change in the crystals of a metal–organic
framework with pendant allyl thioether units in response to Pd species
was discovered. The color change (from light yellow to orange/brick
red) can be triggered by Pd species at concentrations of a few parts
per million and points to the potential use of these crystals in colorimetric
detection and quantification of Pd­(II) ions. The swift color change
is likely due to the combined effects of the multiple functions built
into the porous framework: the carboxyl groups for bonding with Zn­(II)
ions to assemble the host network and the thioether and alkene functions
for effective uptake of the Pd­(II) analytes (e.g., via the alkene–Pd
interaction). The resultant loading of Pd (and other noble metal)
species into the porous solid also offers rich potential for catalysis
applications, and the alkene side chains are amenable to wide-ranging
chemical transformations (e.g., bromination and polymerization), enabling
further functionalization of the porous networks.