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

Abstract

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 {[Pr<inf>4</inf>N][WS<inf>4</inf>Cu<inf>3</inf>(CN)<inf>2</inf>]}<inf>n</inf> (1), {[Pr<inf>4</inf>N][WS<inf>4</inf>Cu<inf>4</inf>(CN)<inf>3</inf>]}<inf>n</inf> (2), {[Pr<inf>4</inf>N][WOS<inf>3</inf>Cu<inf>3</inf>(CN)<inf>2</inf>]}<inf>n</inf> (3), {[Bu<inf>4</inf>N][WOS<inf>3</inf>Cu<inf>3</inf>(CN)<inf>2</inf>]}<inf>n</inf> (4) and {[Bu<inf>4</inf>N][MoOS<inf>3</inf>Cu<inf>3</inf>(CN)<inf>2</inf>]}<inf>n</inf> (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 [WS<inf>4</inf>Cu<inf>3</inf>]+ and single CN- bridges. 2 is fabricated from 6-connected planar 'open' clusters [WS<inf>4</inf>Cu<inf>4</inf>]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 [WOS<inf>3</inf>Cu<inf>3</inf>]+ linked by single CN- bridges, but containing the different cations [Pr<inf>4</inf>N]+ and [Bu<inf>4</inf>N]+, respectively. 5 is constructed from nest-shaped clusters [MoOS<inf>3</inf>Cu<inf>3</inf>]+ 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 ([Pr<inf>4</inf>N]+ vs. [Bu<inf>4</inf>N]+) 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.