Robust Heterogeneous Photocatalyst for Visible-Light-Driven Hydrogen Evolution Promotion: Immobilization of a Fluorescein Dye-Encapsulated Metal–Organic Cage on TiO₂

Abstract

The design of artificial photocatalytic devices that simulates the ingenious and efficient photosynthetic systems in nature is promising. Herein, a metal−organic cage [Pd 6 (NPyCzPF) 12 ] 12+ (MOC-PC6) integrating 12 organic ligands NPyCzBP and 6 Pd 2+ catalytic centers is designed, which is well defined to include organic dye fluorescein (FL) for constructing a supramolecular photochemical molecular device (SPMD) FL@MOC-PC6. Photoinduced electron transfer (PET) between MOC-PC6 and the encapsulated FL has been observed by steady-state and time-resolved emission spectroscopy. FL@MOC-PC6 is successfully heterogenized with TiO 2 by a facile sol−gel method to achieve a robust heterogeneous FL@MOC-PC6-TiO 2 . The close proximity between the Pd 2+ catalytic site and FL included in the cage enables PET from the photoexcited FL to Pd 2+ sites through a powerful intramolecular pathway. The photocatalytic hydrogen production assessments of the optimized 4 wt % FL@MOC-PC6-TiO 2 demonstrate an initial H 2 production rate of 2402 μmol g −1 h −1 and a turnover number of 4356 within 40 h, enhanced by 15-fold over that of a homogeneous FL@MOC-PC6. The effect of the MOC content on photocatalytic H 2 evolution (PHE) is investigated and the inefficient comparison systems, such as MOC-PC6, MOC-PC6-TiO 2 , FL-sensitized MOC-PC6/FL-TiO 2 , and analogue FL/MOC-PC6-TiO 2 with free FL, are evaluated. This study provides a creative and distinctive approach for the design and preparation of novel heterogeneous SPMD catalysts based on MOCs.

Controllable Visible-Light-Driven Syngas Evolution by a Ternary Titania Hybrid Sacrificial System with a Photosensitive Metal–Organic PdII Cage and ReI Catalyst

“…However, a further increase in the MOC-Q2 content (>6.5 wt %) conversely resulted in a decrease in activity because the extra photosensitive molecules on the semiconductor surface could aggregate and cause energy loss owing to the unfavorable intermolecular electron migration, − and meanwhile the increase of organic components brought about the decrease of TiO 2 crystallinity and thus reduced the charge transfer efficiency. This phenomenon was also observed in our previous work. ,, Moreover, the AQYs of ReP/TiO 2 -MOC-Q2 with 4.5, 6.5, and 8.5 wt % MOC content were determined to be 0.28, 0.87, and 0.62% at 450 nm, respectively (Table S2), in agreement with the trend of their photocatalytic activities.…”

“…This phenomenon was also observed in our previous work. 39,45,46 Moreover, the AQYs of ReP/TiO 2 -MOC-Q2 with 4.5, 6.5, and 8.5 wt % MOC content were determined to be 0.28, 0.87, and 0.62% at 450 nm, respectively (Table S2), in agreement with the trend of their photocatalytic activities.…”

PdS Quantum Dots as a Hole Attractor Encapsulated into the MOF@Cd0.5Zn0.5S Heterostructure for Boosting Photocatalytic Hydrogen Evolution under Visible Light

“…The 2D nanomaterials with thickness ranging from a few nanometers to tens of nanometers and lateral dimension up to various centimeters have been the subject of intensive research over the past few years. The 3D nanostructures are described as complex structures assembled from 0D, 1D, 2D, or multiscale nanocomponents, , where 0D MOFs due to their porous structure allowing more catalytic sites to be exposed, largely avoiding the aggregation of materials, particularly shorting the distance of photogenerated electrons to reach the substrate, thereby further improving charge separation and transfer. − However, charge carriers that can reach the catalyst surface are still limited, which limits the production of photocatalytic hydrogen. Therefore, it is necessary to develop other methods to achieve a further leap.…”

Direct Z-Scheme Heterojunction Catalysts Constructed by Graphitic-C3N4 and Photosensitive Metal-Organic Cages for Efficient Photocatalytic Hydrogen Evolution

“…Our group designed a non-photosensitive MOC-PC6 and a photosensitive MOC-Q1, and combined them with semiconductor matrixes including TiO 2 [ 29 ] and g-C 3 N 4 [ 30 , 31 ] for enhancing their performances. In 2021, we synthesized a M 2 L 4 type photosensitive metal-organic cage MOC-Q2 with light-harvesting ligands and catalytic Pd 2+ centers ( Scheme 1 ).…”