Coordination Synergy between Iridium Photosensitizers and Metal Nanoclusters Leading to Enhanced CO2 Cycloaddition under Mild Conditions.

The achievement of photocatalytic CO2 and epoxide cycloaddition under mild conditions such as room temperature and atmospheric pressure is important for green chemistry, which can be achieved by developing coordination synergies between catalysts and photosensitizers. In this context, we exploit the use of coordinate bonds to connect pyridine-appended iridium photosensitizers and catalysts for CO2 cycloaddition, which is systematically demonstrated by 1H nuclear magnetic resonance titration and X-ray photoelectron spectroscopic measurements. It is shown that the hybrid Ir(Cltpy)2/Mn2Cd4 photocatalytic system with coordination synergy exhibits excellent catalytic performance (yield ≈ 98.2%), which is 3.75 times higher than that of the comparative Ir(Cltpy-Ph)2/Mn2Cd4 system without coordination synergy (yield ≈ 26.2%), under mild conditions. The coordination between the Mn2Cd4 catalyst and the Ir(Cltpy)2 photosensitizer enhances the light absorption and photoresponse properties of the Mn2Cd4 catalyst. This has been confirmed through transient photocurrent, electrochemical impedance, and electron paramagnetic tests. Consequently, the efficiency of cycloaddition was enhanced by utilizing mild conditions.

Novel salenCo(iii) photoinitiators and their application for cycloaddition of carbon dioxide.

Carbon dioxide (CO2) is a renewable carbon resource that can be effectively used in the production of polycarbonate (PPC) and cyclic carbonate (CPC) through open-loop copolymerization with epoxides and CO2. SalenCo(iii) can successfully break the carbon-oxygen link between propylene oxide (PO) and CO2. On this basis, we prepared four different types of photosensitive salenCo(iii) complexes and investigated their catalytic copolymerization of CO2 and PO. The results show that the catalytic performance of 1,2-cyclohexamediamine complexes is better than that of 1,2-o-phenylenediamine complexes. The catalytic efficiency of salenCo(iii) catalyst increases with the expansion of the photosensitive conjugate system. In addition, the introduction of light can improve the catalytic efficiency. When we increased the power of the external light source from 100 W to 200 W, the TON of the catalyst [C4] increased by nearly 50%.

Novel Mn4-Co2 nanocluster@photosensitizers/SalenCo(iii) catalyze the copolymerization of carbon dioxide and propylene oxide.

In general, transition metals (TMs) often facilitate highly efficient catalysis. Herein, we synthesized a series of nanocluster composite catalysts by combining with photosensitizers and SalenCo(iii) for the first time and studied the catalytic copolymerization of CO2 and propylene oxide (PO). Systematic experiments have shown that the selectivity of copolymerization products can be improved by the nanocluster composite catalysts, and their synergistic effects significantly improved the photocatalytic performance of carbon dioxide copolymerization. At specific wavelengths, I@S1 can achieve a TON of 536.4, which is 2.26 times that of I@S2. Interestingly, in the photocatalytic products of I@R2, CPC reached 37.1%. These findings provide a new idea for the study of TM nanocluster@photosensitizers for carbon dioxide photocatalysis, and may provide guidance for exploring low cost and highly efficient carbon dioxide emission reduction photocatalysts.

MPA-CdTe quantum dots as "on-off-on" sensitive fluorescence probe to detect ascorbic acid via redox reaction.

Mercaptopropionic acid (MPA) capped CdTe quantum dots (MPA-CdTe QDs) were synthesized in aqueous medium by hydrothermal method, which modified by Fe3+ could be used as a fluorescent probe to detect ascorbic acid (AA). MPA-CdTe QDs fluorescence probe could be used as successive sensor for metal ions and AA with "on-off-on" process. The fluorescence of QDs was quenched after adding Fe3+ to MPA-CdTe QDs. Then, the fluorescence of the Fe3+@MPA-CdTe QDs can be sensitively turned on by AA to give an "on-off-on" fluorescence response according to the oxidation-reduction between Fe3+ and AA. There was a linear relationship between fluorescence intensity quenching value and the concentration of Fe3+ in the range of 2-10 µM since Fe3+ sensitively reacted with CdTe QDs. The linear detection range for AA was 0.1-1 µM with a limit of detection of 6.6 nM. The principle is proved by fluorescence emission spectroscopy, nuclear magnetic resonance spectroscopy. The proposed method is successfully used to detect the AA in human plasma sample.

The salen based chemosensors for highly selective recognition of Zn2+ ion.

Two novel salen based chemosensors have been successfully synthesized. UV-vis absorption, fluorescence emission spectroscopy and cyclic voltammetry (CV) were exploited to investigate their recognition toward various metal ions, including Na+, K+, Mg2+, Al3+, Zn2+, Ag+, Pb2+, Co2+, Li+, Ba2+, Ca2+, Cd2+, La3+, Cu2+ and Mn2+ ions. The results indicated that the sensor L1 and L2 exhibited highly selective and sensitive recognition for Zn2+ ions. The binding stoichiometry ratio of L1-Zn2+/L2-Zn2+ were recognized as 4:1 by the method of Job's plot. Meanwhile, this investigation is confirmed by 1H NMR. These results indicated that L1 and L2 can be applied as chemosensor for the detection of Zn2+ ion.