Sulfur in the pore: tailoring coordination networks for metal uptake, sensing and other applications

We utilize thioether and thiol groups for functionalizing metal-organic frameworks to facilitate the uptake and inclusion of metal species.1-3 For example, free-standing, accessible thiol functions (-SH) have been installed in a robust, porous coordination network for wide-ranging reactivities and properties in the solid state. The framework are assembled by reacting ZrCl4 with 2,5-dimercapto-1,4-benzenedicarboxylic acid (H2DMBD) featuring the hard carboxyl and soft thiol functions. The resultant Zr-DMBD framework is of the UiO-66 topology, with the carboxyl bonded to the hard Zr(IV) or Al(III) center, and the thiol groups decorating the pores. The thiol-laced Zr-DMBD crystals lower Hg(II) concentration in water below 0.01 ppm, and effectively take up Hg from the vapor phase. The Zr-DMBD solid also features a nearly white photoluminescence that is distinctly quenched after Hg uptake. The carboxyl-thiol combination thus illustrates the wider applicability of the hard-and-soft strategy for functional frameworks. A wide range of other metal species such as PdCl2 and AgBF4 can also be uploaded into the porous networks via interactions with the thioether/thiol groups. Preliminary results of utilizing the uploaded metal species for potential applications in precious metal retrieval, sensing and catalysis will also be discussed.