Investigations on post-synthetically modified UiO-66-NH2 for the adsorptive removal of heavy metal ions from aqueous solution

• Novel functionalised Zr-based MOFs prepared using post-synthetic modification.
• Pendant sulphur-containing groups have been introduced into the pores of the MOFs.
• Functionalization markedly improved heavy metal removal efficiency.
• High performance material with facile preparative route and good aqueous stability.

The metal organic framework UiO-66-NH2 has been post-synthetically modified to introduce thiourea, isothiocyanate and isocyanate functionalities without compromising the structural and thermal stability of the parent framework. 1H NMR and IR spectroscopies have been used to monitor the extent of framework functionalization. UiO-66, UiO-66-NH2 and the new functionalized frameworks UiO-66-NHC(S)NHMe, UiO-66-NHC(S)NHPh, UiO-66-NCS and UiO-66-NCO have been studied as adsorbents for the capture of a range of heavy metals from homoionic aqueous solution, with a view towards applications in environmental remediation. Functionalization markedly improved metal removal efficiency up to 99% with calculated maximum adsorption capacities of 49, 117, 232 and 769 mg/g for Cd2+, Cr3+, Pb2+ and Hg2+ respectively for UiO-66-NHC(S)NHMe.

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