Jia-Xing Jiang

Tunable Organic Photocatalysts for Visible-Light-Driven Hydrogen Evolution

Photocatalytic hydrogen production from water offers an abundant, clean fuel source, but it is challenging to produce photocatalysts that use the solar spectrum effectively. Many hydrogen-evolving photocatalysts are active in the ultraviolet range, but ultraviolet light accounts for only 3% of the energy available in the solar spectrum at ground level. Solid-state crystalline photocatalysts have light absorption profiles that are a discrete function of their crystalline phase and that are not always tunable. Here, we prepare a series of amorphous, microporous organic polymers with exquisite synthetic control over the optical gap in the range 1.94-2.95 eV. Specific monomer compositions give polymers that are robust and effective photocatalysts for the evolution of hydrogen from water in the presence of a sacrificial electron donor, without the apparent need for an added metal cocatalyst. Remarkably, unlike other organic systems, the best performing polymer is only photoactive under visible rather than ultraviolet irradiation.

Metal–Organic Conjugated Microporous Polymers

Zwei vielseitige Strategien fur die Herstellung von Metall-organischen konjugierten mikroporosen Polymeren (MO-CMPs) mit Metallen wie Rhenium, Rhodium und Iridium werden beschrieben (siehe Beispiel). Diese Materialien vereinen in sich zwei Merkmale: eine ausgedehnte, unterbrechungsfreie elektronische Konjugation und das Vorhandensein katalytisch aktiver Metallzentren

Band gap engineering in fluorescent conjugated microporous polymers

We report here the synthesis of conjugated microporous polymers (CMPs) based on pyrene building units. The networks are both microporous and highly luminescent. The emission colour and resulting band gap can be fine tuned by introducing different comonomers and by varying the monomer distribution (statistical versus alternating). These materials might find applications in organic electronics, photocatalysis, optoelectronics, or in sensing technologies.

Functional conjugated microporous polymers: from 1,3,5-benzene to 1,3,5-triazine

Conjugated microporous polymers (CMPs) based on the electron-withdrawing 1,3,5-triazine node (TCMPs) were synthesized by palladium-catalyzed Sonogashira-Hagihara cross-coupling. The porosity in these polymers was found to be comparable to the analogous 1,3,5-connected benzene CMP systems that we reported previously, demonstrating that nodes can be substituted in these amorphous materials in a rational manner, much as for certain crystalline porous metal–organic frameworks. The CO2 adsorption properties of the TCMPs were measured and compared with the corresponding CMPs, and it was found that the TCMP networks adsorbed more CO2 than CMP analogues with comparable BET surface areas. Network TNCMP-2 showed the highest surface area (995 m2 g−1) and a CO2 uptake of 1.45 mmol g−1 at 1 bar at 298 K. The band gap in these triazine-based CMPs could also be engineered through copolymerization with other functional monomers.

Shedding Light on Structure-Property Relationships for Conjugated Microporous Polymers: The Importance of Rings and Strain.

The photophysical properties of insoluble porous pyrene networks, which are central to their function, differ strongly from those of analogous soluble linear and branched polymers and dendrimers. This can be rationalized by the presence of strained closed rings in the networks. A combined experimental and computational approach was used to obtain atomic scale insight into the structure of amorphous conjugated microporous polymers. The optical absorption and fluorescence spectra of a series of pyrene-based materials were compared with theoretical time-dependent density functional theory predictions for model clusters. Comparison of computation and experiment sheds light on the probable structural chromophores in the various materials.

Hypercrosslinked microporous polymers based on carbazole for gas storage and separation

Two hypercrosslinked microporous organic polymer networks from carbazole derivatives have been synthesized via Friedel–Crafts alkylation using a formaldehyde dimethyl acetal crosslinker promoted by anhydrous FeCl3. Both of the polymer networks are stable in various solvents and thermally stable. The polymer network FCTCz produced from a dendritic carbazole building block shows much higher Brunauer–Emmet–Teller specific surface area of 1845 m2 g−1 than the dicarbazolic polymer network of FCBCz (1067 m2 g−1). FCTCz exhibits a high carbon dioxide uptake ability of 4.63 mmol g−1 at 1.13 bar and 273 K with a hydrogen uptake ability of 1.94 wt% (1.13 bar/77 K). In addition, both of the polymer networks exhibit good ideal CO2/N2 selectivity (26–29) and CO2/CH4 selectivity (5.2–5.8) at 273 K. These results demonstrated that this kind of polymer network is a very promising candidate for potential applications in post-combustion carbon dioxide capture and sequestration technology.

BODIPY-containing porous organic polymers for gas adsorption

A series of BODIPY-containing microporous organic polymers was synthesized via a Sonogashira–Hagihara cross-coupling reaction of a BODIPY derivative with triple polymerisable groups and a range of aryl–alkyne monomers. All of the polymers show high isosteric heats of CO2 adsorption (23.3–27.3 kJ mol−1) because the incorporation of heteroatoms (N, B, F) from the BODIPY unit into the polymer skeleton enhanced the binding affinity between the pore wall and CO2 molecules. The aryl–alkyne monomer has a large influence on the surface area and CO2 adsorption performance of the resulting polymers. The polymer BDPCMP-3 shows a high Brunauer–Emmett–Teller specific surface area of up to 725 m2 g−1, while BDPCMP-2 with a low surface area of 582 m2 g−1 shows a high CO2 uptake ability of 2.25 mmol g−1 at 1.13 bar/273 K with a CO2/N2 adsorption selectivity of 32.3.

In situ bubble template-assisted synthesis of phosphonate-functionalized Rh nanodendrites and their catalytic application

The controllable synthesis of branched noble metal nanostructures has attracted significant attention as it provides excellent catalytic activity and durability to these metal nanostructures. In the present study, a facile and effective complexation–reduction strategy was developed for synthesizing Rh nanodendrites with hippocampus tail-like branches (Rh-NDHTs) using N2H4·H2O as a reductant and multiphosphonate molecule with small molecular weight as a complexant and functional agent. During the synthesis, the coordination interaction between multiphosphonate and RhCl3 as well as the hydrazine decomposition reaction (H2NNH2 = N2 + 2H2) catalyzed by the freshly formed Rh nanocrystals play important roles in the generation of Rh-NDHTs. Moreover, phosphonate functionalization of Rh-NDHTs was simultaneously achieved during the course of the synthesis, originating from the strong adsorption of multiphosphonate on the Rh surface. When used as a heterogeneous catalyst for the o-phenylenediamine oxidation reaction, the phosphonate-functionalized Rh-NDHTs exhibited enhanced catalytic efficiency and durability as compared to the commercially available Rh nanocrystals, attributing to their extraordinary morphological and interfacial properties.