An electron-rich metal-organic framework for highly efficient photocatalytic reduction of Cr(VI)

A metal-organic framework, Cd-TIPA, was synthesized using cadmium ion and a stretched triangular rigid N-containing ligand tris-(4-imidazolylphenyl)amine (TIPA) as a strong electron donor. Cd-TIPA features an unusual 3D structure of two sets of layers linked in an interpenetration arrangement, resulting in framework with 26.1% porosity. Cd-TIPA possesses a long luminescence lifetime of 5.76 is and Mott -Schottky measurements indicate Cd-TIPA is a representative n-type semiconductor. Cd-TIPA features a potential of the conduction band (LUMO) level (-1.30 V vs. NHE), which is more negative than that of Cr203-/Cr3+, thus providing the theoretical possibility of reduction. The valence band (HOMO) level is estimated as 1.37 V based on a Tauc plot, indicating a higher oxidation ability for H2O. The observable quenching effect of Cr203- anions on the emission of a suspension of Cd-TIPA indicates the efficient electron transfer. As expected, Cd-TIPA functioned as an efficient catalyst for heterogeneous photocatalytic reduction of Cr203- with high catalytic efficiency (93%) in 12 min. (C) 2020 Elsevier B.V. All rights reserved.