Two Cu(i) coordination polymers based on a new benzimidazolyl-tetrazolyl heterotopic ligand for visible-light-driven photocatalytic dye degradation

Abstract

Two Cu(I) coordination polymers (CPs), namely, [Cu^I(DBPT)(H₂O)]_n (HDBPT = 3,5-di((1H-benzeimidazol-yl)phenyl)-2H-tetrazole, CP 1) and [Cu^I(DBPT)·DMF]_n (CP 2), were constructed based on a new N-containing heterotopic triangular ligand. CP 1 is a 2D network consisting of binuclear secondary building units (SBUs). The 2D layers are connected by strong hydrogen bonds to form a 3D supramolecular framework. CP 2 possesses a 3D framework based on binuclear SBUs and features a (3,6)-connected rtl topology. Both CP 1 and CP 2 have high stability in water in the pH range from 3–13 and exhibit energy band gaps of 2.70 and 2.79 eV, respectively, which indicate their possibility in visible-light-driven photocatalysis. The photocatalytic results show that both CP 1 and CP 2 display good activity for MLB degradation in the presence of H₂O₂ as an oxidant under visible light irradiation. A mechanistic investigation indicated that the photogenerated holes trapped by Cu(I) generate Cu(II). Cu(II) may be involved in a Fenton-like CuI/CuII redox reaction to generate ˙OH. Thus, holes and ˙OH contribute to the degradation of MLB. In addition, the degradation product of MLB was further studied by LC-MS, which indicates that MLB is almost degraded to small molecules.