Self-Assembly of Biarsenate Capped Keggin Arsenomolybdates with Tetravanadium Substitution for Photocatalytic Degradation of Organic Dyes

Four new POMs biarsenate(III) capped Keggin arsenomolybdates with tetravanadium(IV) substituted (bix)[H3As2IIIAsVMo8V4IVO40][Cu(bix)]2·3H2O(1), [{HAs2IIIAsV Mo8V4IVO40}{Cu(bib)}2][Cu(bib)]2(2), [{As2IIIAsVMo8V4IVO40}{Cu3(tib)2(H2O)2}] [Cu(tib)(H2O)]2·4H2O(3), and [HAs2IIIAsVMo8V4IVO40][Cu2(bih)]2(4) (bix = 1,4-bis(imidazol-1-ylmethyl) benzene; bib = 1,3-bis (imidazol-1-ylmethyl)benzene; tib = 1,3,5-tris(1-imidazolyl)benzene; bih = 1,6-bis(imidazol-1-ylmethyl)hexane) were prepared. Compound 1 contains a {Cu(bix)}2 fragment and [H3As2IIIAsVMo8V4IVO40]2– cluster, which form a 1D chain by Cu1···O6 3.215 Å. The {Cu(bib)}2 chain threads the rectangular loop of other {Cu(bib)}2 connected with the [HAs2IIIAsVMo8V4IVO40]4– cluster, resulting in 1D+1D extended into 3D frameworks in 2. Compound 3 contains two types of 1D chains based on [As2IIIAsVMo8V4IVO40]5– cluster and copper-tib complexes. The feature of 4 is that the [HAs2IIIAsVMo8V4IVO40]4– cluster as a hexa-node is surrounded by {Cu2(bih)}2 units by terminal and bridging oxygen atoms (Ot and Ob) forming 3D POMOFs with Schläfli symbol of {4.64.8}2{42.613}{44.64.82}2. Additionally, the photocatalytic properties of 1–4 exhibit excellent degradation activity for methylene blue (MB) under UV light, which were ascribed to main active component in generating ·O2–. The photocatalytic reaction kinetics and mechanism of 1–4 were investigated in detail. Furthermore, luminescence properties of 1–4 were also studied.