Abstract

Acute Cr VI water pollution due to anthropogenic activities is an increasing worldwide concern. The high toxicity and mobility of Cr VI makes necessary to develop dual adsorbent/ion-reductive materials that are able to capture Cr VI and transform it efficiently to less hazardous Cr III . The accurate description of the chromium speciation at the adsorbent/ion-reductive matrix is key to assess whether Cr VI is completely reduced to Cr III , or if its incomplete transformation led to the stabilization of highly reactive Cr V transient species within the material. With this goal in mind, a dual ultraviolet visible and electron paramagnetic spectroscopy approach has been applied to determine the Cr speciation within Zr-based metal-organic frameworks (MOFs). Our findings point out that the generation of defect positions at Zr-MOFs boost Cr VI adsorption, whilst the presence of reductive groups at the organic linkers play a key role to stabilize it as Cr III isolated and/or clustered ions.