A new generation of visible-light-active photocatalysts—The alkaline earth metal bismuthates: Syntheses,compositions, structures,and properties

Semiconductor materials containing bismuth have attracted the attention of researchers over the past several decades, as a result of their high photocatalytic activity in various reactions and/or high efficiency in their photoelectric conversion of solar energy. This interest originated from the observations that bismuth-containing semiconductors have a sufficiently small bandgap, which makes them sensitive to radiation in the visible spectral range; thus, visible-light-active materials. Among the various bismuth-containing semiconductor materials, the bismuthates of alkaline earth metals are distinguished and describe into separate groups. This article reviews research on the known methods of obtaining bismuthates of various alkaline earth metals (magnesium, calcium, strontium, and barium), and further analyzes their composition, structure, and visible-light-active photocatalytic activity.     

Solvothermal modification of graphitic C3N4 with Ni and Co phthalocyanines: Structural,optoelectronic and surface properties

Nanocomposites for photocatalytic applications were obtained by alchothermal modification of g-C₃N₄ with cobalt(ii) and nickel(ii) phthalocyanine complexes. The nanocomposites demonstrated higher photocatalytic activity than the bare matrix and stability under actinic irradiation. In the optoelectronic structure of the composites, the E_g value of the g-C₃N₄ matrix increased to 3.05 eV, while for MPc agents, it decreased from 1.96 to 1.82 eV.     

Photochemical and Electrochemical Strategies for Hydrodefluorination of Fluorinated Organic Compounds

Hydrodefluorination (HDF) is a very important fundamental transformation for conversion of the C−F bond into the C−H bond in organic synthesis. In the past decade, much progress has been achieved with HDF through the utility of low-valent metals, transition-metal complexes and main-group Lewis acids. Recently, novel methods have been introduced for this purpose through photo- and electrochemical pathways, which are of great significance, due to their considerable environmental and economical advantages. This Review highlights the HDF of fluorinated organic compounds (FOCs) through photo- and electrochemical strategies, along with mechanistic insights.     

Stable Heterometallic Cluster‐Based Organic Framework Catalysts for Artificial Photosynthesis

A series of stable heterometallic Fe₂M cluster‐based MOFs ( NNU‐31‐M , M=Co, Ni, Zn) photocatalysts are presented. They can achieve the overall conversion of CO₂ and H₂O into HCOOH and O₂ without the assistance of additional sacrificial agent and photosensitizer. The heterometallic cluster units and photosensitive ligands excited by visible light generate separated electrons and holes. Then, low‐valent metal M accepts electrons to reduce CO₂, and high‐valent Fe uses holes to oxidize H₂O. This is the first MOF photocatalyst system to finish artificial photosynthetic full reaction. It is noted that NNU‐31‐Zn exhibits the highest HCOOH yield of 26.3 μmol g^?1 h^?1 (selectivity of ca. 100 %). Furthermore, the DFT calculations based on crystal structures demonstrate the photocatalytic reaction mechanism. This work proposes a new strategy for how to design crystalline photocatalyst to realize artificial photosynthetic overall reaction.     

Thin film photocatalysis for environmental remediation: A status review

This review accounts, various metal oxide and metal sulfide thin films available for photodegradation of several organic compounds. Due to difficulties in recycling and to avoid rigorous recollection of powder catalysts, the thin film catalyst are gaining rapid attention for photocatalytic applications. The semiconducting thin films are growing as promising photocatalyst for water treatment. This review focuses mainly on the photocatalytic activity of metal oxide thin films in terms of its stability, charge transport and absorption properties. Thin film photocatalyst provides the increased efficiency and cost reduction of device. Furthermore, this review summarizes some key factors regarding the enhancement in photocatalytic performance of thin films.     

Light-Induced Tetrazole-Quinone 1,3-Dipolar Cycloadditions

Quinones were firstly used as dipolarophiles in a photoclick 1,3-cycloaddition with 2,5-diaryltetrazoles, as photoactivatable predipoles, providing a novel and efficient access to three types of pyrazole-fused quinones (indazoledione derivatives). Distinctive features of this protocol include the use of light as the unique reagent and readily available, stable, and easy to handle starting materials and good to excellent yields. Photophysical and electrochemical properties of the quinones and their potential application as photoredox catalysts are also detailed.     

NIR Light-Induced ATRP for Synthesis of Block Copolymers Comprising UV-Absorbing Moieties

NIR exposure at 790 nm activated photopolymerization of monomers comprising UV-absorbing moieties by using [Cu^II/(TPMA)]Br₂ (TPMA=tris(2-pyridylmethyl)amine) in the ppm range and an alkyl bromide as initiator. Some of them comprised structural elements selected either from those showing proton transfer or photocycloaddition upon UV excitation. Polymers obtained comprise living end groups serving as macroinitiator for controlled synthesis of block copolymers with relatively narrow molecular weight distributions. Chromatographic results indicated formation of block copolymers produced by this synthetic approach. Free-radical polymerization of monomers pursued for comparison exhibited the expected broader dispersity of molecular weight compared to photo-ATRP. Polymerization of these monomers by UV photo-ATRP failed on the contrary to NIR photo-ATRP demonstrating the UV-filter function of the monomers. This work conclusively provides a new approach for the polymerization of monomers comprising UV-absorbing moieties through photo-ATRP in the NIR region. This occurred in a simple and efficient pathway. However, studies also showed that not all monomers chosen successfully proceeded in the NIR photo-ATRP protocol.     

Cyanine-Flavonol Hybrids for Near-Infrared Light-Activated Delivery of Carbon Monoxide

Carbon monoxide (CO) is an endogenous signaling molecule that controls a number of physiological processes. To circumvent the inherent toxicity of CO, light-activated CO-releasing molecules (photoCORMs) have emerged as an alternative for its administration. However, their wider application requires photoactivation using biologically benign visible and near-infrared (NIR) light. In this work, a strategy to access such photoCORMs by fusing two CO-releasing flavonol moieties with a NIR-absorbing cyanine dye is presented. These hybrids liberate two molecules of CO in high chemical yields upon activation with NIR light up to 820 nm and exhibit excellent uncaging cross-sections, which surpass the state-of-the-art by two orders of magnitude. Furthermore, the biocompatibility and applicability of the system in vitro and in vivo are demonstrated, and a mechanism of CO release is proposed. It is hoped that this strategy will stimulate the discovery of new classes of photoCORMs and accelerate the translation of CO-based phototherapy into practice.     

Manipulating Host-Guest Charge Transfer of a Water-Soluble Double-Cavity Cyclophane for NIR-II Photothermal Therapy

Water-soluble small organic photothermal agents (PTAs) over NIR-II biowindow (1000–1350 nm) are highly desirable, but the rarity greatly limits their applications. Based on a water-soluble double-cavity cyclophane GBox-4⁴⁺ , we report a class of host–guest charge transfer (CT) complexes as structurally uniform PTAs for NIR-II photothermal therapy. As a result of its high electron-deficiency, GBox-4⁴⁺ can bind different electron-rich planar guests with a 1 : 2 host/guest stoichiometry to readily tune the CT absorption band that extends to the NIR-II region. When using a diaminofluorene guest substituted with an oligoethylene glycol chain, the host–guest system realized both good biocompatibility and enhanced photothermal conversion at 1064 nm, and was then exploited as a high-efficiency NIR-II PTA for cancer cell and bacterial ablation. This work broadens the potential applications of host–guest cyclophane systems and provides a new access to bio-friendly NIR-II photoabsorbers with well-defined structures.     

Z型复合催化剂g-C3N4/Vo-ZnO光催化活性的研究

随着科学技术的不断进步和经济的快速发展,人类对自然资源的需求量越来越大,在开发利用自然资源的同时,大量的有机污染物也随之进入自然环境.这些物质不仅污染环境、破坏生态,更对人类的生活和健康带来了巨大的威胁.研究证实,半导体光催化剂在光照条件下可以破坏有机污染物的分子结构,最终将其氧化降解成CO2、H2O或其它不会对环境产生二次污染的小分子,从而净化水质.近年来,有关光催化降解有机污染物的报道日益增多. ZnO作为一种广泛研究的光催化降解材料,因其无毒、低成本和高效等特点而具有一定的应用前景.但是ZnO较大的禁带宽度(3.24 eV)导致其只能吸收紫外光部分,而对可见光的吸收效率很小,极大地制约了其实际应用.除此之外, ZnO受光激发产生的电子-空穴分离效率较低、光催化过程中的光腐蚀严重也是制约其实际应用的重要因素.为了提高ZnO的光催化活性和稳定性,本文合成了用g-C3N4修饰的氧空位型ZnO(g-C3N4/Vo-ZnO)复合催化剂,在有效调控ZnO半导体能带结构的同时,通过负载一定量的g-C3N4以降低光生电子-空穴对的复合速率和反应过程中ZnO的光腐蚀,增强催化剂的光催化活性和稳定性.本文首先合成前驱体Zn(OH)F,然后焙烧三聚氰胺和Zn(OH)F的混合物得到g-C3N4/Vo-ZnO复合催化剂,并采用电子顺磁共振波谱(EPR)、紫外-可见光谱(UV-vis)、高分辨透射电镜(HRTEM)和傅里叶变换红外光谱(FT-IR)等表征了它们的结构及其性质. EPR结果表明,ZnO焙烧后具有一定浓度的氧空位,导致其禁带宽度由3.24 eV降至3.09 eV,因而提高了ZnO对可见光的吸收效率. UV-vis结果显示, Vo-ZnO复合g-C3N4后对可见光的吸收显著增强. HRTEM和FT-IR结果均表明, g-C3N4纳米片和Vo-ZnO颗粒之间通过共价键形成了强耦合,这对g-C3N4/Vo-ZnO复合催化剂中光生载流子的传送和光生电子-空穴对的有效分离起到重要作用.可见光催化降解甲基橙(MO)和腐殖酸(HA)的实验进一步证明, g-C3N4/Vo-ZnO复合材料具有较好的光催化活性,优于单一的g-C3N4或Vo-ZnO材料.同时还发现, g-C3N4的负载量对光催化活性有显著影响,当氮化碳的负载量为1 wt%时,所制材料具有最高的光催化活性：可见光照射60 min后,MO降解率可达到93%, HA降解率为80%.复合材料光催化活性的增强一方面是因为氧空位的形成减小了ZnO的禁带宽度,使得ZnO对可见光的吸收能力大大增强;另一方面, g-C3N4和Vo-ZnO的能带符合了Z型催化机理所需的有效能带匹配,使得光生电子-空穴对得到了有效的分离,从而提高了光催化活性.降解MO的循环实验表明, g-C3N4/Vo-ZnO催化剂具有很好的稳定性且不容易发生光腐蚀.与此同时,我们对比了用不同方法制备的g-C3N4/ZnO材料的催化性能.结果显示,本文制备的g-C3N4/Vo-ZnO复合材料具有更好的降解效率.总体而言,对于降解有机污染物, g-C3N4/Vo-ZnO可能是一个更为有效可行的催化体系.此外,本文也为设计与制备其他新型光催化剂提供了一条新的思路.