Copper-Containing Polyoxometalate-Based Metal-Organic Framework as a Catalyst for the Oxidation of Silanes: Effective Cooperative Catalysis by Metal Sites and POM Precursor

Catalytic Synthesis of Silanols by Hydroxylation of Hydrosilanes: From Chemoselectivity to Enantioselectivity

As a crucial class of functional molecules in organosilicon chemistry, silanols are found valuable applications in the fields of modern science and will be a potentially powerful framework for biologically active compounds or functional materials. It has witnessed an increasing demand for non-natural organosilanols, as well as the progress in the synthesis of these structural features. From the classic preparative methods to the catalytic selective oxidation of hydrosilanes, electrochemical hydrolysis of hydrosilanes, and then the construction of the most challenging silicon-stereogenic silanols. This review summarized the progress in the catalyzed synthesis of silanols via hydroxylation of hydrosilanes in the last decade, with a particular emphasis on the latest elegant developments in the desymmetrization strategy for the enantioselective synthesis of silicon-stereogenic silanols from dihydrosilanes.

Metallocavitins as Advanced Enzyme Mimics and Promising Chemical Catalysts

The supramolecular approach is becoming increasingly dominant in biomimetics and chemical catalysis due to the expansion of the enzyme active center idea, which now includes binding cavities (hydrophobic pockets), channels and canals for transporting substrates and products. For a long time, the mimetic strategy was mainly focused on the first coordination sphere of the metal ion. Understanding that a highly organized cavity-like enzymatic pocket plays a key role in the sophisticated functionality of enzymes and that the activity and selectivity of natural metalloenzymes are due to the effects of the second coordination sphere, created by the protein framework, opens up new perspectives in biomimetic chemistry and catalysis. There are two main goals of mimicking enzymatic catalysis: (1) scientific curiosity to gain insight into the mysterious nature of enzymes, and (2) practical tasks of mankind: to learn from nature and adopt from its many years of evolutionary experience. Understanding the chemistry within the enzyme nanocavity (confinement effect) requires the use of relatively simple model systems. The performance of the transition metal catalyst increases due to its retention in molecular nanocontainers (cavitins). Given the greater potential of chemical synthesis, it is hoped that these promising bioinspired catalysts will achieve catalytic efficiency and selectivity comparable to and even superior to the creations of nature. Now it is obvious that the cavity structure of molecular nanocontainers and the real possibility of modifying their cavities provide unlimited possibilities for simulating the active centers of metalloenzymes. This review will focus on how chemical reactivity is controlled in a well-defined cavitin nanospace. The author also intends to discuss advanced metal–cavitin catalysts related to the study of the main stages of artificial photosynthesis, including energy transfer and storage, water oxidation and proton reduction, as well as highlight the current challenges of activating small molecules, such as H2O, CO2, N2, O2, H2, and CH4.

Synthesis and Structure of a Copper-Based Functional Network for Efficient Organic Dye Adsorption

In the work, by incorporating polyoxometalates (POMs) into a copper(II)-based network, a novel three-dimensional (3D) porous framework, [Cu₁₇Cl₃(trz)₁₂]H₃[GaW₁₂O₄₀]·9H₂O (Cu-GaW-TRZ), was successfully prepared and explored for the adsorption of dyes. The adsorption capacity of Cu-GaW-TRZ was calculated as 13.11 mg/g, and the dye adsorption rate equaled 96.2% for the adsorption of methylene blue (MB). Furthermore, this recyclable adsorbent is stable enough without obvious loss of adsorption capacity for at least five runs. Meanwhile, the structure of the macropores is suitable for the entry of large molecular dyes, and [GaW₁₂O₄₀]^5- also can achieve efficient adsorption for cationic dyes. The results displayed a pseudo-second-order kinetic model and were well matched for MB adsorption onto Cu-GaW-TRZ. The free energy, entropy, and enthalpy of the thermodynamic parameters for the adsorption of MB were calculated, which revealed that the adsorption process was befitting for the adsorption of MB.

Applications of Viologens in Organic and Inorganic Discoloration Materials

Viologen derived from 4,4'-bipyridine has attracted much attention because of its color changing properties with electron transfer, unique redox stability and structural diversity. These characteristics have led to its successful use in various applications, in particular in color-changing materials. In the past few years, researchers have been working on the syntheses of viologen-based color-changing functional materials, and such materials have been widely used in many fields. In photochromic materials, it is used as anti-counterfeiting material; in thermochromic, it is used as memory storage material, and in electrochromic, it is used as a battery material. This Review discusses the progress of viologen in organic and inorganic discoloration materials in recent years. The syntheses of viologen and its derivatives are summarized, and its application in the field of discoloration materials is introduced.