A metal-organic cage incorporating multiple light harvesting and catalytic centres for photochemical hydrogen production.

Sha Chen,Jianying Shi,Cheng-Yong Su,Lei Zhang,Mei Pan,Jing Guo,Fang Zhao,Kang Li,Yan-Zhong Fan

doi:10.1038/ncomms13169

Abstract

Photocatalytic water splitting is a natural but challenging chemical way of harnessing renewable solar power to generate clean hydrogen energy. Here we report a potential hydrogen-evolving photochemical molecular device based on a self-assembled ruthenium–palladium heterometallic coordination cage, incorporating multiple photo- and catalytic metal centres. The photophysical properties are investigated by absorption/emission spectroscopy, electrochemical measurements and preliminary DFT calculations and the stepwise electron transfer processes from ruthenium-photocentres to catalytic palladium-centres is probed by ultrafast transient absorption spectroscopy. The photocatalytic hydrogen production assessments reveal an initial reaction rate of 380 μmol h−1 and a turnover number of 635 after 48 h. The efficient hydrogen production may derive from the directional electron transfers through multiple channels owing to proper organization of the photo- and catalytic multi-units within the octahedral cage, which may open a new door to design photochemical molecular devices with well-organized metallosupramolecules for homogenous photocatalytic applications.

Highlights

Photocatalytic water splitting is a natural but challenging chemical way of harnessing renewable solar power to generate clean hydrogen energy
In addition to the metal-organic frameworks (MOFs)-like advantages such as assembly of multiple, functional organic ligands and metal centres, metal-organic cages/containers (MOCs) merit consideration because they may be able to organize the active subcomponents in a specific fashion to achieve collaborative and synergistic functions reminiscent of photosystems I and II, and accomplish catalysis in homogeneous conditions
The solution dynamics study has confirmed that MOC-16 is the sole thermodynamically stable product in solution, where appearance of one set of 1H NMR pattern is indicative of high O-symmetry for the [Pd6(RuL3)8]28 þ cage[38,39]

Summary

Introduction

Photocatalytic water splitting is a natural but challenging chemical way of harnessing renewable solar power to generate clean hydrogen energy. The efficient hydrogen production may derive from the directional electron transfers through multiple channels owing to proper organization of the photo- and catalytic multi-units within the octahedral cage, which may open a new door to design photochemical molecular devices with well-organized metallosupramolecules for homogenous photocatalytic applications. Visible light-driven water splitting to produce hydrogen is considered as an attractive alternative energy source leading to solar energy conversion and storage In this context, crystalline metal-organic frameworks (MOFs) have been widely studied in photocatalytic water splitting in heterogeneous conditions[1,2,3] owing to the advantages that verstaile organic chromophores and catalytically active metal centres can be integrated into the framework, or, loaded into the pores. To the best of our knowledge, such a self-assembled MOC as the single hydrogenevolving PMD made up of multiple photo- and catalytic metal centres has not been reported yet, Duan et al.[40] have utilized MOCs for photocatalytic H2 generation via encapsulation of organic dyes

Methods

Results

Conclusion