Metal-organic redox vehicles to encapsulate organic dyes for photocatalytic protons and carbon dioxide reduction

The application of metal–organic molecular hosts as “molecular flasks” has precipitated a surge of interest in the reactivity and properties of molecules within well-defined spaces. Here we report an approach to construct supramolecular systems for photo-catalytic hydrogen production and carbon dioxide reduction by encapsulating an organic dye molecule into the pocket of the redox-active metal–organic macrocycle. The assembled Ni3L3 tricycle consists of three ligands and three nickel ions that alternately connect together. The special geometry enforces the distortion of the square planar coordinated configuration, and the coordination of the sulphur atoms enables the modification of redox potentials suitable for proton reduction and carbon dioxide reduction. The supramolecular systems that have fluorescein molecules being encapsulated as the photosensitive guests feature efficient activity for the photocatalytic carbon dioxide conversion and production reduction. The new reaction pathways within the confined space demonstrate the power of the supramolecular system over related systems.