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CO2 hydrogenation to formic acid is full of challenges due to the high stability of both H2 and CO2. For a long time, unrecyclable bases had been widely used in CO2 hydrogenation to shift the reaction equilibrium by the formation of formate, while a low turnover number (TON) was obtained in the absence of a base. Herein, an efficient method of hydrogenation of CO2 to formic acid in water without consumption of a base is realized. The base can be easily regenerated by the transformation between imidazolium bicarbonate ionic liquid and imidazolium formate in the presence of CO2. A TON of up to 364 249could be achieved in the CO2 hydrogenation performed in an aqueous solution. Formic acid is isolatable with a separation yield of up to 86.8%. The catalyst and base could be recycled simultaneously and their activities remained quite well preserved in a five-cycle experiment. [ABSTRACT FROM AUTHOR]

In this work, cyclic (alkyl)(amino)carbene copper ((CAAC)Cu) catalyzed aerobic oxidation of aldehydes in water at room temperature has been reported. Good to excellent yields were obtained using different substrates. A possible reaction mechanism was proposed, in which (CAAC)Cu dioxygen activates the C–H bond of aldehyde with a low barrier of 10.6 kcal mol−1. [ABSTRACT FROM AUTHOR]

Transportation and transformation of photogenerated carriers during the photocatalytic process of graphitic carbon nitride (g-C3N4) are restricted by the low surface area and insufficient charge separation efficiency. Exfoliation of g-C3N4 into few layered nanosheets is an ideal method to resolve these problems. This work provides a green and facile method to prepare g-C3N4 nanosheets with outstanding photocatalytic H2O2 production ability via NaClO hydrothermal treatment. This simple process could readily be extended to a kilogram scale. XRD, UV-vis, N2 adsorption, SEM, TEM, XPS, O2-TPD, EIS and PL were used to characterize the catalysts. Taking advantages of both the oxidation effect of ClO− and the intercalation effect of Na+, the obtained g-C3N4 nanosheets display a specific surface area as high as 145.6 m2 g−1. The carbon vacancies formed by NaClO treatment could promote the O2 adsorption capacity of the catalyst and then activate the adsorbed O2 molecule. The charge separation efficiency and redox ability of g-C3N4 nanosheets are also promoted compared with bulk g-C3N4, leading to the obviously improved H2O2 production ability. In addition, the obtained g-C3N4 nanosheets show higher photocatalytic performance than that prepared by chemical oxidation exfoliation, thermal exfoliation and intercalation exfoliation methods. This confirms that NaClO hydrothermal treatment is a more green, facile and effective method to prepare g-C3N4 nanosheet photocatalysts with outstanding performance. [ABSTRACT FROM AUTHOR]

A series of Ca2Sr(PO4)2:Ce3+,Mn2+,Na+ phosphors were synthesized by a high-temperature solid-state reaction. Under ∼320 nm excitation, the Ce3+ and Mn2+ co-doped phosphors exhibit two emission bands peaking at 370 and 645 nm, which originate from 5d–4f and 3d–3d transitions of Ce3+ and Mn2+, respectively. Luminescence properties, diffuse reflectance spectra, and decay curves indicate that energy transfer (ET) occurs from Ce3+ to Mn2+, and the ET efficiency reaches its maximum (91%) at an Mn2+ content of 0.35. The diffuse reflectance spectrum shows that the co-doped phosphors have strong absorption around 320 nm, which is good for the anti-aging ability of an agricultural film. The absolute quantum efficiency of the Ca1.6Sr(PO4)2:0.15Ce3+,0.10Mn2+,0.15Na+ phosphor is ∼94%. And the co-doped phosphors exhibit good stability in water. Therefore, Ca2Sr(PO4)2:Ce3+,Mn2+,Na+ phosphors have potential application as a light conversion material in agricultural films. [ABSTRACT FROM AUTHOR]

A comprehensive description of the complicated dynamics of excited state evolution and charge transfer at the photochemical interface in dye-sensitized solar cells is crucial to understand the mechanism of converting solar photons to clean electricity, providing an informative basis for the future development of advanced organic materials. By selecting two triarylamine-based organic donor–acceptor dyes characteristic of the respective benzoic acid and cyanoacrylic acid anchors, in this paper we reveal stepwise excited state relaxations and multiple-state electron injections at a realistic titania/dye/electrolyte interface based upon ultrafast spectroscopic measurements and theoretical simulations. Density functional theory (DFT) and time-dependent DFT calculations show that the optically generated “hot” excited state of the dye molecules can undergo a significant conformational relaxation via multistage torsional motions, and thereby transform into an equilibrium quinonoid structure characteristic of a more planar conjugated backbone. A set of kinetic parameters derived from the target analysis of femtosecond transient absorption spectra have been utilized to estimate the electron injection yield, which is in good accord with the maximum of external quantum efficiencies. [ABSTRACT FROM AUTHOR]