Nanostructured charge transfer complex of CuTCNQF4 for efficient photo-removal of hexavalent chromium

Abstract

The high toxicity of hexavalent chromium warrants the development of efficient catalysts that could reduce chromium into relatively non-toxic trivalent chromium species. Pristine charge transfer complexes of the MTCNQ family (M = Cu or Ag; TCNQ = 7,7,8,8-tetracyanoquinodimethane) have previously failed to catalyse the reduction of Cr⁶⁺ to Cr³⁺. We demonstrate that due to the outstanding electron transfer properties of one of the fluorinated derivatives of MTCNQ, i.e., 7,7,8,8-tetracyano-2,3,5,6-tetraflouroquinodimethane (CuTCNQF₄), it is able to catalyse the reduction of hexavalent chromium in aqueous solution at room temperature. We further demonstrate that the semiconducting nature of these organic charge transfer complexes allows CuTCNQF₄ to act as an outstanding material for the reductive photo-removal of hexavalent chromium under UV photoexcitation conditions. Such materials are likely to play an important role in photoactive electron transfer reactions.