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

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.

The Redox Coupling Effect in a Photocatalytic RuII‐PdII Cage with TTF Guest as Electron Relay Mediator for Visible‐Light Hydrogen‐Evolving Promotion

“…As we can see, the H 2 evolution of MOC‐16 without TTF shows a production rate of 129 μmol h −1 in the initial 3 h, but drops obviously in the following procedure. A total H 2 production of 1597 μmol is reached after 47 h, representing a turnover number (TON) of 605 (based on Pd 2+ catalytic centers, 2.64 μmol) which is comparative with our previous study (TON=635 in 48 h) conducted in a 100 mL DMSO–H 2 O solution with successive 3 h recycling procedure . In the presence of TTF, the H 2 production capacity is overall improved, but the evolution rates show close dependence on the amount of TTF.…”

“…Along this line, synthetic strategies have been reported to engineer functional coordination innerspace of nanocages via incorporation of either redox‐active or photoactive centers, thus generating MOC‐based photocatalytic host–guest systems to imitate natural photosynthesis, where the spatially separated electron and/or energy transfer processes can facilitate photocatalytic water/H 2 S splitting, as well as other chemical transformations. To achieve efficient conversion from solar energy to chemical energy in such host–guest systems, one of the fundamental factors is to control the photo‐induced redox events in the confined chemical nanospace .…”

“…A prototypical model is the hetero‐metallic Ru II ‐Pd II nanocage ([Pd 6 (RuL 3 ) 8 ] 28+ , MOC‐16, L=2‐(pyridin‐3‐yl)‐1 H ‐imidazo[4,5‐f][1,10]phenanthroline) incorporating multiple photo, redox and catalytic centers, providing a 3 nm sized coordination nanospace for guest encapsulation (Figure ). Owing to its native photosensitizing and photocatalytic activities, we believe that, not only intramolecular charge transfer, but also host–guest electron transfer process should be possible. Therefore, a redox coupling interaction may be anticipated if an adequate redox guest is applied.…”

Amorphous‐TiO2‐Encapsulated CsPbBr3 Nanocrystal Composite Photocatalyst with Enhanced Charge Separation and CO2 Fixation

“…In this circumstance, to pursue a high‐efficiency photocatalytic system, suitable band alignment and panchromatic absorption behavior of the light harvester appear to be major concerns. Accordingly, a variety of semiconductor materials have been developed as available candidates for photocatalysis, including traditional alternatives such as metal oxides (e.g., TiO 2 , perovskite oxides), metal sulfides, C 3 N 4 , carbons, metal organic frameworks . Morover, our group for the first time has reported that the CsPbBr 3 quantum dot, a representative lead halide perovskite material, was able to conduct the photocatalytic reduction of CO 2 .…”

Amino‐Induced 2D Cu‐Based Metal–Organic Framework as an Efficient Heterogeneous Catalyst for Aerobic Oxidation of Olefins

“…Metal–organic polyhedra (MOPs) as crystalline coordination materials that are constituted by metal ions and organic ligands . Owing to their unique features, such as permanent porosity and unsaturated metal centers, MOPs have shown great potential for applications in drug delivery, gas adsorption and storage, chemical sensors, and catalysis . As a common ligand isophthalic acid and its corresponding derivatized ligands have been widely used to prepare MOP materials .…”