An Amino-Thiophene Functionalized Metal-Organic Framework on Fabric for Selective Extraction, Recovery, and Passive...

The steadily increasing use of gold and the limited gold reserves have instigated a significant research effort to develop materials with efficient gold recovery. However, most works focus only on the uptake of Au ions, ignoring Au nanoparticles, which are increasingly used in various applications and represent a critical source of Au. Furthermore, the reported gold recovery studies involve powder-form materials that cannot be easily retrieved after the sorption process, thus making them unattractive for real, large-scale applications. The present work reports a Zr-(IV) metal-organic framework (MOF) with a defective microporous structure and amino-thiophene functional groups, which exhibit strong interactions with Au species. The MOF was immobilized on cotton fabric via an in situ method to create an easily retrievable bulk sorbent composite, which was investigated in detail for its sorption properties toward Au ions and Au nanoparticles (AuNPs). The immobilized sorbent showed relatively fast sorption kinetics (<1 and 3 h for Au ions and AuNPs, respectively), impressive sorption capacities (883.5 and 43.4 mg Au/g for Au ions and AuNPs, respectively), capability for capturing AuNPs irrespective of their coating and size and high recovery (>85%) of gold either as ions or AuNPs from genuine water samples. The latter property allowed the use of the MOF-fabric sorbent for the development of the first passive sampling sorbent phase for the long-term monitoring or recovery of AuNPs from natural waters. Notably, the sorbent was highly effective for the selective recovery of Au (∼97%) from an electronic waste simulant under flow conditions. The reusability of the MOF, in a composite form with calcium alginate, as Au sorbent was demonstrated under flow conditions for several cycles, indicating the potential of the material for Au separation applications. Overall, the reported sorbent offers a practical and cost-effective means for efficiently recovering ionic and nanoparticle Au species from complex water and wastewater media.