中空全固态Z型异质结光催化剂的研究进展

中空结构材料由于比表面积大、密度低和电荷传输距离短等特点,在光催化反应中具有巨大的应用价值. Z型光催化剂具有宽光谱响应、高稳定性、高光生载流子的分离效率以及强氧化还原能力等优点,受到了广泛关注.然而,由于Z型多元组分和中空结构不稳定,设计并制备高效稳定的中空全固态Z型光催化剂仍是一大挑战.本文综合评述了近年来中空全固态Z型光催化剂的种类、构筑策略及性能等方面的研究进展,并进一步展望了其在未来应用中面临的问题与挑战,最后归纳总结了其设计与发展方向,为高效稳定光催化剂的设计提供了思路.     

Nano-scaled titanium dioxide – properties and use in coatings with special functionality

Nano-scaled titanium dioxides are used as UV-absorbers and to obtain certain color effects in pigmented coatings. For this they are generally required to have good phototresistivity. This is accomplished by doping of the crystal lattice with other elements than titania and by surface treatment with layers of inorganic substances. Currently the use of photoreactive nano-scaled titanias is being studied to formulate self cleaning and antimicrobial coatings.     

Fast Visible-Light 3D Printing of Conductive PEDOT:PSS Hydrogels

Functional inks for light-based 3D printing are actively being searched for being able to exploit all the potentialities of additive manufacturing. Herein, a fast visible-light photopolymerization process is showed of conductive PEDOT:PSS hydrogels. For this purpose, a new Type II photoinitiator system (PIS) based on riboflavin (Rf), triethanolamine (TEA), and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is investigated for the visible light photopolymerization of acrylic monomers. PEDOT:PSS has a dual role by accelerating the photoinitiation process and providing conductivity to the obtained hydrogels. Using this PIS, full monomer conversion is achieved in less than 2 min using visible light. First, the PIS mechanism is studied, proposing that electron transfer between the triplet excited state of the dye (³Rf*) and the amine (TEA) is catalyzed by PEDOT:PSS. Second, a series of poly(2-hydroxyethyl acrylate)/PEDOT:PSS hydrogels with different compositions are obtained by photopolymerization. The presence of PEDOT:PSS negatively influences the swelling properties of hydrogels, but significantly increases its mechanical modulus and electrical properties. The new PIS is also tested for 3D printing in a commercially available Digital Light Processing (DLP) 3D printer (405 nm wavelength), obtaining high resolution and 500 µm hole size conductive scaffolds.     

Photoinduced Nickel-Catalyzed Carbon–Heteroatom Coupling**

Herein, we report visible light-promoted single nickel catalysis for diverse carbon–heteroatom couplings under mild conditions. This mild, general, and robust method to couple diverse nitrogen, oxygen, and sulfur nucleophiles with aryl(heteroaryl)/alkenyl iodides/bromides exhibits a wide functional group tolerance and is applicable to late-stage modification of pharmaceuticals and natural products. On the base of preliminary mechanistic studies, a Ni^I/Ni^III cycle via the generation of active Ni^I complexes that appear from homolysis of Ni^II−I rather than Ni^II−aryl bond was tentatively proposed.     

Pyrazine Derivative as Supramolecular Host for Immobilization of Palladium Nanoparticles for Efficient Suzuki Coupling

Palladium nanoparticles (NPs) have been extensively explored as unique catalyst for carbon-carbon coupling reactions. Nonetheless, because of extreme tendency of nanoparticles to undergo agglomeration, the immobilization of these metal NPs on organic frameworks is an important area of research. The present investigation demonstrates the synthesis of pyrazine derivative PYZ - TA as a supramolecular host for holding co-released Pd NPs derived from the original catalyst (Pd(II)) under standard Suzuki coupling. Unprecedent, physical bars are not required to capture Pd NPs within the pores of supramolecular host. The as obtained catalyst PYZ - TA@Pd exhibits high potential to undergo self-assembly in solid as well as in liquid state. The PYZ - TA@Pd ensemble shows high catalytic activity and recyclability (up to seven cycles) in Suzuki-Miyaura coupling reactions using low palladium loading and provides the corresponding products in excellent yields (up to 98 %). Therefore, this study provides an efficient strategy to develop an easy to synthesize palladium centered solid catalyst through coordination between organic host and Pd NPs.     

In Situ Synthesis of Cu3P/P-Doped g-C3N4 Tight 2D/2D Heterojunction Boosting Photocatalytic H2 Evolution†

Heterojunction design in a two-dimensional (2D) fashion has been deemed beneficial for improving the photocatalytic activity of g-C₃N₄ because of the promoted interfacial charge transfer, yet still facing challenges. Herein, we construct a novel 2D/2D Cu₃P nanosheet/P-doped g-C₃N₄ (PCN) nanosheet heterojunction photocatalyst (PCN/Cu₃P) through a simple in-situ phosphorization treatment of 2D/2D CuS/g-C₃N₄ composite for photocatalytic H₂ evolution. We demonstrate that the 2D lamellar structure of both CuS and g-C₃N₄ could be well reserved in the phosphorization process, while CuS and g-C₃N₄ in-situ transformed into Cu₃P and PCN, respectively, leading to the formation of PCN/Cu₃P tight 2D/2D heterojunction. Owing to the large contact area provided by intimate face-to-face 2D/2D structure, the PCN/Cu₃P photocatalyst exhibits significantly enhanced charge separation efficiency, thus achieving a boosted visible-light-driven photocatalytic behavior. The highest rate for H₂ evolution reaches 5.12 μmol·h^–1, nearly 24 times and 368 times higher than that of pristine PCN and g-C₃N₄, respectively. This work represents an excellent example in elaborately constructing g-C₃N₄-based 2D/2D heterostructure and could be extended to other photocatalyst/co-catalyst system.