The Redox Coupling Effect in a Photocatalytic Ru^II -Pd^II Cage with TTF Guest as Electron Relay Mediator for Visible-Light Hydrogen-Evolving Promotion

A nanocage coupling effect from a redox Ru^II -Pd^II metal-organic cage (MOC-16) is demonstrated for efficient photochemical H₂ production by virtue of redox-guest modulation of the photo-induced electron transfer (PET) process. Through coupling with photoredox cycle of MOC-16, tetrathiafulvalene (TTF) guests act as electron relay mediator to improve the overall electron transfer efficiency in the host-guest system in a long-time scale, leading to significant promotion of visible-light driven H₂ evolution. By contrast, the presence of larger TTF-derivatives in bulk solution without host-guest interactions results in interference with PET process of MOC-16, leading to inefficient H₂ evolution. Such interaction provides an example to understand the interplay between the redox-active nanocage and guest for optimization of redox events and photocatalytic activities in a confined chemical nanoenvironment.