Alkylamino-terephthalate ligands stabilize 8-connected Zr4+ MOFs with highly efficient sorption for toxic Se species

Abstract

Zirconium(IV) metal organic frameworks (MOFs) with low net connectivity and available intra-framework sorption sites constitute excellent sorbents for toxic anions. To expand this family of highly promising sorbents, it would be desired to develop new synthetic strategies aiming towards such materials. Here we show that the utilization of terephthalate ligands with small to medium size alkyl-amino functional groups comprises an effective approach towards microporous Zr⁴⁺ MOFs with 8-connected frameworks. The new MOFs were proved the most effective Se(IV) and Se(VI) sorbents ever reported, with exceptional sorption capacities (up to 272 mg_Se(IV) g⁻¹ and 290 mg_Se(VI) g⁻¹), reusability, rapid sorption kinetics (≤3 min) and capability to sorb efficiently these anions in a very wide pH range (1–10), even in the presence of various competitive anions. The MOFs also display highly efficient sorption capability for the particularly toxic SeCN⁻, with such property demonstrated for the first time for MOF materials.