UiO-67-derived bithiophene and bithiazole MIXMOFs for luminescence sensing and removal of contaminants of emerging concern in wastewater

Solvent-assisted ligand exchange in the zirconium metal-organic framework (MOF) UiO-67 [Zr6O4(OH)(4)(PhPh)(6); H2PhPh = biphenyl-4,4'-dicarboxylic acid] with the heterocyclic linkers H(2)TpTp (2,2'-bithiophene-5,5'-dicarboxylic acid) and H(2)TzTz (2,2'-bithiazole-5,5'-dicarboxylic acid) in an equimolar [Zr6] : linker ratio led to the corresponding MIXMOFs UiO-67-TpTp [Zr6O4(OH)(4)(PhPh)(5)(TpTp)] and UiO-67-TzTz [Zr6O4(OH)(4)(PhPh)(5)(TzTz)]. Both MOFs have been thoroughly characterized in the solid state. They show the same structural topology and crystal structure of UiO-67, as confirmed by powder X-ray diffraction. Their BET specific surface area is lower than that of their parent material (1700 and 1310 m(2) g(-1) for UiO-67-TpTp and UiO-67-TzTz, respectively, vs. 1877 m(2) g(-1) for UiO-67), while the thermal stability of UiO-67 (T-dec = 819 K) is maintained. The diluted inclusion, in the UiO-67 3D framework, of luminescent heterocyclic linkers emitting in the blue-green visible region induces luminescence in the final MOFs (emission lambda(max) = 442 and 420 nm for UiO-67-TpTp and UiO-67-TzTz, respectively), preventing self-quenching effects caused by the proximity of the emitters in the crystal structure. Both MOFs have been tested as sensors for contaminants of emerging concern (CECs) in water: an emission intensity increase has been observed when suspended in contact with diclofenac sodium, fluoxetine, ibuprofen and sulfamethoxazole. In particular, UiO-67-TzTz has shown a linearly increasing trend for a specific concentration range (up to 30-40 mu M for diclofenac, fluoxetine and ibuprofen; up to 100 mu M for sulfamethoxazole). UiO-67-TzTz also behaves as an adsorbent vs. diclofenac, with a maximum adsorption capacity (X-m) of 62.5 mg g(-1). These findings pave the way to the practical utilization of UiO-67-TzTz as a multifunctional material (i.e. CECs luminescent sensor and adsorbent at one time) for environmental remediation.

Automated summary

Solvent-assisted ligand exchange in Zr-MOF UiO-67 led to the synthesis of mixed MOFs UiO-67-TpTp and UiO-67-TzTz with lower BET specific surface area but maintained thermal stability. These MOFs show potential as sensors for contaminants of emerging concern in water, with UiO-67-TzTz also exhibiting adsorption capabilities.