Single cyanide-bridged Mo(W)/S/Cu cluster-based coordination polymers: Reactant- and stoichiometry-dependent syntheses, effective photocatalytic properties

The systematic study on the reaction variables affecting single cyanide-bridged Mo(W)/S/Cu cluster-based coordination polymers (CPs) is firstly demonstrated. Five anionic single cyanide-bridged Mo(W)/S/Cu cluster-based CPs {[Pr₄N][WS₄Cu₃(CN)₂]}_n (1), {[Pr₄N][WS₄Cu₄(CN)₃]}_n (2), {[Pr₄N][WOS₃Cu₃(CN)₂]}_n (3), {[Bu₄N][WOS₃Cu₃(CN)₂]}_n (4) and {[Bu₄N][MoOS₃Cu₃(CN)₂]}_n (5) were prepared by varying the molar ratios of the starting materials, and the specific cations, cluster building blocks and central metal atoms in the cluster building blocks. 1 possesses an anionic 3D diamondoid framework constructed from 4-connected T-shaped clusters [WS₄Cu₃]⁺ and single CN^- bridges. 2 is fabricated from 6-connected planar 'open' clusters [WS₄Cu₄]²⁺ and single CN^- bridges, forming an anionic 3D architecture with an "ACS" topology. 3 and 4 exhibit novel anionic 2-D double-layer networks, both constructed from nest-shaped clusters [WOS₃Cu₃]⁺ linked by single CN^- bridges, but containing the different cations [Pr₄N]⁺ and [Bu₄N]⁺, respectively. 5 is constructed from nest-shaped clusters [MoOS₃Cu₃]⁺ and single CN^- bridges, with an anionic 3D diamondoid framework. The anionic frameworks of 1-5, all sustained by single CN^- bridges, are non-interpenetrating and exhibit huge potential void volumes. Employing differing molar ratios of the reactants and varying the cluster building blocks resulted in differing single cyanide-bridged Mo(W)/S/Cu cluster-based CPs, while replacing the cation ([Pr₄N]⁺ vs. [Bu₄N]⁺) was found to have negligible impact on the nature of the architecture. Unexpectedly, replacement of the central metal atom (W vs. Mo) in the cluster building blocks had a pronounced effect on the framework. Furthermore, the photocatalytic activities of heterothiometallic cluster-based CPs were firstly explored by monitoring the photodegradation of methylene blue (MB) under visible light irradiation, which reveals that 2 exhibits effective photocatalytic properties.