Photocatalytic Hydrosilylation over Pt@UiO-66-NH2: Enhanced Activity and Polymerization Kinetics

Metal-organic frameworks (MOFs) have shown great research and application value in various types of hydrosilylation reactions. However, studies on photocatalysis-induced hydrosilylation using MOFs are extremely rare. Metal nanoparticles (MNPs)@MOFs are extensively studied for their excellent structural tunability and photocatalytic activity, but there are few reports on their application in photocatalytic hydrosilylation. Here, a novel photocatalyst consisting of platinum (Pt) nanoparticles immobilized in a MOF framework is synthesized and used for photocatalytic hydrosilylation. The effects of various factors on hydrosilylation conversion are investigated, including catalyst concentration, substrate ratio, and irradiation intensity. Furthermore, the photoreactivity of the synthesized Pt catalyst is evaluated in the presence of different concentrations of 2-chlorothixanthone as a photosensitizer. It is noteworthy that the conversion of the reaction increases with increasing catalyst concentration or photosensitizer concentration, whereas increasing the polymethylhydrosiloxane content does not lead to a significant increase in conversion. This study demonstrates the potential of MNPs@MOFs as efficient photocatalysts for photoinduced hydrosilylation reactions and paves the way for future applications in this area.

Hierarchical Double-Shelled CoP Nanocages for Efficient Visible-Light-Driven CO2 Reduction

Visible-light-driven photocatalytic CO₂ reduction is considered an appealing strategy to mitigate the energy crisis and environmental issues, whereas the reactivity is limited due to the difficulties in activation of inert CO₂ molecule and efficient transportation of photoinduced carriers. Herein, we report the design of novel Fe doped CoP hierarchical double-shelled nanocages (Fe-CoP HDSNC) via a MOF-templated approach for highly efficient visible-light-driven CO₂ reduction. The unique hierarchical double-shelled hollow architectures can greatly shorten the charge transfer distances and also expose abundant reactive sites. Moreover, Fe atoms doping is able to reduce the CO₂ activation energy barrier through stabilizing the *COOH intermediates and promote the CO desorption by destabilizing the CO* adduct. As expected, the Fe-CoP HDSNC achieves an unprecedented catalytic efficiency in visible-light-driven CO₂ reduction with an up to 3.25% apparent quantum yield and 90.3% CO selectivity, superior to most of the state-of-the-art photocatalysts under comparable conditions. More importantly, the Fe-CoP HDSNC is also highly effective under diluted CO₂ atmosphere, suggesting the practicability of the present photocatalytic system.

Tunable linear donor–π–acceptor conjugated polymers with a vinylene linkage for visible-light driven hydrogen evolution

Extending the in-plane conjugation or/and increasing the electron push–pull interaction of linear D–π–A polymers with a vinylene linkage could broaden the visible-light absorption band, promote the charge separation and transfer and the photocatalytic hydrogen production.

Controlling 1T/2H heterophase junctions in the MoS2 microsphere for the highly efficient photocatalytic hydrogen evolution

The 1T/2H heterophase junction MoS2 microspheres were fabricated for a highly efficient photocatalytic hydrogen evolution.

Supramolecular Energy Materials

Self-assembly is a bioinspired strategy to craft materials for renewable and clean energy technologies. In plants, the alignment and assembly of the light-harvesting protein machinery in the green leaf optimize the ability to efficiently convert light from the sun to form chemical bonds. In artificial systems, strategies based on self-assembly using noncovalent interactions offer the possibility to mimic this functional correlation among molecules to optimize photocatalysis, photovoltaics, and energy storage. One of the long-term objectives of the field described here as supramolecular energy materials is to learn how to design soft materials containing light-harvesting assemblies and catalysts to generate fuels and useful chemicals. Supramolecular energy materials also hold great potential in the design of systems for photovoltaics in which intermolecular interactions in self-assembled structures, for example, in electron donor and acceptor phases, maximize charge transport and avoid exciton recombination. Possible pathways to integrate organic and inorganic structures by templating strategies and electrodeposition to create materials relevant to energy challenges including photoconductors and supercapacitors are also described. The final topic discussed is the synthesis of hybrid perovskites in which organic molecules are used to modify both structure and functions, which may include chemical stability, photovoltaics, and light emission.

Molecular Engineering of Fully Conjugated sp2 Carbon-Linked Polymers for High-Efficiency Photocatalytic Hydrogen Evolution

The diverse nature of organic precursors offers a versatile platform for precisely tailoring the electronic properties of semiconducting polymers. In this study, three fully conjugated sp² carbon-linked polymers have been designed and synthesized for photocatalytic hydrogen evolution under visible-light illumination, by copolymerizing different C₃ -symmetric aromatic aldehydes as knots with the 1,4-phenylene diacetonitrile (PDAN) linker through a C=C condensation reaction. The hydrogen evolution (HER) is achieved at a maximum rate of 30.2 mmol g^-1  h^-1 over a polymer based on 2,4,6-triphenyl-1,3,5-triazine units linked by cyano-substituted phenylene, with an apparent quantum yield (AQY) of 7.20 % at 420 nm. Increasing the degree of conjugation and planarity not only extends visible-light absorption, but also stabilizes the fully conjugated sp² -carbon-linked donor-acceptor (D-A) polymer. Incorporating additional electron-withdrawing triazine units into the D-A polymer to form multiple electron donors and acceptors can greatly promote exciton separation and charge transfer, thus significantly enhancing the photocatalytic activity.

Hot π-Electron Tunneling of Metal-Insulator-COF Nanostructures for Efficient Hydrogen Production

A metal-insulator-semiconductor (MIS) photosystem based on covalent organic framework (COF) semiconductors was designed for robust and efficient hydrogen evolution under visible-light irradiation. A maximal H₂ evolution rate of 8.42 mmol h^-1  g^-1 and a turnover frequency of 789.5 h^-1 were achieved by using a MIS photosystem prepared by electrostatic self-assembly of polyvinylpyrrolidone (PVP) insulator-capped Pt nanoparticles (NPs) with the hydrophilic imine-linked TP-COFs having =C=O-H-N= hydrogen-bonding groups. The hot π-electrons in the photoexcited n-type TP-COF semiconductors can be efficiently extracted and tunneled to Pt NPs across an ultrathin PVP insulating layer to reduce protons to H₂ . Compared to the Schottky-type counterparts, the COF-based MIS photosystems give a 32-fold-enhanced carrier efficiency, attributed to the combined enhancement of photoexcitation rate, charge separation, and oxidation rate of holes accumulated in the valence band of the TP-COF semiconductor.

A fluorescent conjugated polymer photocatalyst based on Knoevenagel polycondensation for hydrogen production

An organic polymer photocatalyst (p-P) for hydrogen production was designed and synthesized through Knoevenagel condensation with a high yield.

Nanofabrication of a Solid-State, Mesoporous Nanoparticle Composite for Efficient Photocatalytic Hydrogen Generation

Room-temperature self-assembly was used to fabricate a periodic array of uniformly sized Al³⁺ -doped SiO₂ nanoparticles (Al-SiO₂ NPs, 20-30 nm). The uniform mesoporous structure was suitable for uniformly incorporating and distributing Pt nanoparticles (PtNPs), which were used as hydrogen-evolution catalysts in artificial photosynthetic systems, without agglomeration during the catalytic reaction. When the surfaces of the Al-SiO₂ NPs were covered with an organic photocatalyst (2-phenyl-4-(1-naphthyl)quinolinium ion, QuPh⁺ -NA), each PtNP was surrounded by multiple QuPh⁺ -NA ions. The structure allowed the PtNP to receive multiple electrons from QuPh^. -NA molecules, which were generated by reduction of the photoexcited state of QuPh⁺ -NA ions (QuPh^. -NA^{. +} ) with β-dihydronicotinamide adenine dinucleotide (NADH), thereby resulting in efficient photocatalytic H₂ evolution.