Acid-Modulated Synthesis of Novel π-Conjugated Microporous Polymers for Efficient Metal-Free Photocatalytic Hydrogen Evolution

Simple synthetic modifications that tune the molecular structures, thereby the properties of the molecules, are of topical interest. Herein, we report the synthesis of two novel cationic rosaniline-based conjugated microporous polymers (CMPs) from identical monomers via simple acid modulation (Acetic acid and BF₃ ⋅ Et₂O). The condensation reaction of rosaniline with 2,4,6-triformylphloroglucinol in acetic acid renders β-ketoenamine-linked CMP ( CMP-A ) while changing the acid to BF₃ ⋅ Et₂O, the linkages transform to enol and undergoes BF₂-complexation, leading to boranil CMP ( CMP-B ). BF₂-functionalities in boranil CMP significantly modified the optical and functional properties compared to β-ketoenamine-linked CMP. The cationic-delocalization along with the extended π-delocalization supported by chromophoric BF₂-groups allow CMP-B to exhibit broad absorption spanning the visible to Near-Infrared region (NIR). The absorption red-edge of CMP-B appears around 1277 nm (optical band gap ∼1.58 eV) while CMP-A displays at 981 nm (optical band gap ∼1.83 eV). Most interestingly, as a photocatalyst, CMP-B catalyzes hydrogen evolution with a superior rate of 252 μmol g⁻¹ over CMP-A (100 μmol g⁻¹). It is about 2.5 times higher performance. The transient photocurrent measurements, electrochemical impedance data, and in-depth mott-Schottky analysis demonstrate that the BF₂-group in CMP-B generates photoinduced charge carriers and their migration towards the active sites for photocatalysis. These polymers show significant photocatalytic H₂ generation without any supportive metal co-catalyst. The BF₂ complexed building blocks are a unique class of metal-free photocatalysts for hydrogen evolution through green and cost-effective approach.     

An Efficient Palladium-catalyzed Coupling Reaction for the Preparation of Biaryls and Polyaryls

In the case of Pd(Ph3)4 as catalyst and toluene as reaction solvent,the desired biaryls and polyaryls were synthesized in excellent yield and on a large scate.     

In Situ Corrosion Fabrication of NaNbO3/Nb3O7F Heterojunctions with Optimized Band Realignment for Enhanced Photocatalytic Hydrogen Evolution

Heterostructured photocatalysis is a significant issue owing to the unique band alignment, improved spectrum absorption, and enhanced photocatalytic activity. However, the construction of uniform, controllable, and effective heterojunctions is still a huge challenge. Herein, NaNbO₃/Nb₃O₇F heterojunctions are fabricated through an in situ corrosion technique for the first time. The influence of phase transformation on the hydrogen evolution reaction (HER) activity is investigated systematically in terms of photocatalytic water splitting for H₂ production. Interestingly, the band realignment and good interfacial contact endow the NaNbO₃/Nb₃O₇F heterojunctions with a high HER activity (43.3 mmol g⁻¹ h⁻¹), which is about 2.4 times that of pure Nb₃O₇F and 1.36 times that of pure NaNbO₃. The results may provide some new insights into the corrosion technique and HER activity of novel heterostructured catalysts.     

Photocatalytic Generation of Hydrogen Radical (H⋅) with GSH for Photodynamic Therapy

As a reactive hydrogen species, the hydrogen radical (H⋅) scarcely sees applications in tumor biological therapy due to the very limited bio-friendly sources of H⋅. In this work, we report that TAF can act as an organic photosensitizer as well as an efficient photocatalytic H⋅ generator with reduced glutathione (GSH) as a fuel. The photoactivation of TAF leads to cell death in two ways including triple amplification of oxidative stress via ferroptosis-apoptosis under normoxia and apoptosis through biological reductions under hypoxia. TAF presents excellent biosafety with ultrahigh photocytotoxicity index at an order of magnitude of 10²–10³ on both normoxic and hypoxic cells. The in vitro data suggest that H⋅ therapy is promising to overcome the challenge of tumor hypoxia at low doses of both photocatalyst and light. In addition, the capability of near-infrared two-photon excitation would benefit broad biological applications.     

Rhodium(III)-Catalyzed C−H/N−H Functionalization with Hydrogen Evolution

A rhodium(III)-catalyzed C−H/N−H bond functionalization of benzimidates with α-chloroaldehydes to afford isoquinolin-3-ol derivatives is reported. No external oxidants are needed in this process, and interestingly, evolution of hydrogen gas is observed.     

Amorphous Manganese–Cobalt Nanosheets as Efficient Catalysts for Hydrogen Evolution Reaction (HER)

Catalysis Surveys from Asia - A facile and efficient electrocatalyst for hydrogen evolution reaction (HER) to produce hydrogen is very important for future energy. In this paper, amorphous...     

A Mild and Efficient Procedure for the Preparation of Chromone-2-carboxylates

Chromone-2-carboxylates are widely used for the pharmacological activity of several of its derivatives1. The general synthesis of such chromone derivates includes two steps (Scheme 1): a Claison condensation of dialkyl oxalate with 2-hydroxyacetophenones to achieve alkyl 3-(2-hydroxyphenyl)-3-oxopropanoates in the presence of NaH, NaOEt, or NaOMe; cyclodehydration of the alkyl 3-(2-hydroxyaryl)-3-oxopropanoates to obtain chromones under acid condition. The total yield of the two steps is q…     

Heterogeneous Photocatalytic Recycling of FeX2/FeX3 for Efficient Halogenation of C−H Bonds Using NaX

Environmental-friendly halogenation of C−H bonds using abundant, non-toxic halogen salts is in high demand in various chemical industries, yet the efficiency and selectivity of laboratory available protocols are far behind the conventional photolytic halogenation process which uses hazardous halogen sources. Here we report an FeX₂ (X=Br, Cl) coupled semiconductor system for efficient, selective, and continuous photocatalytic halogenation using NaX as halogen source under mild conditions. Herein, FeX₂ catalyzes the reduction of molecular oxygen and the consumption of generated oxygen radicals, thus boosting the generation of halogen radicals and elemental halogen for direct halogenation and indirect halogenation via the formation of FeX₃. Recycling of FeX₂ and FeX₃ during the photocatalytic process enables the halogenation of a wide range of hydrocarbons in a continuous flow, rendering it a promising method for applications.     

Directed Evolution of an Iron(II)- and α-Ketoglutarate-Dependent Dioxygenase for Site-Selective Azidation of Unactivated Aliphatic C−H Bonds**

Fe^II- and α-ketoglutarate-dependent halogenases and oxygenases can catalyze site-selective functionalization of C−H bonds via a variety of C−X bond forming reactions, but achieving high chemoselectivity for functionalization using non-native functional groups remains rare. The current study shows that directed evolution can be used to engineer variants of the dioxygenase SadX that address this challenge. Site-selective azidation of succinylated amino acids and a succinylated amine was achieved as a result of mutations throughout the SadX structure. The installed azide group was reduced to a primary amine, and the succinyl group required for azidation was enzymatically cleaved to provide the corresponding amine. These results provide a promising starting point for evolving additional SadX variants with activity on structurally distinct substrates and for enabling enzymatic C−H functionalization with other non-native functional groups.     

An Efficient Mg/SmI_2 Catalytic System for the Intermolecular Deoxygenative Coupling of Amides and Ketones

Ｔｈｅｉｎｔｅｒｍｏｌｅｃｕｌａｒｏｒｉｎｔｒａｍｏｌｅｃｕｌａｒｒｅｄｕｃｔｉｖｅｄｅ ｏｘｙｇｅｎａｔｉｏｎｏｆｃａｒｂｏｎｙｌｃｏｍｐｏｕｎｄｓｔｏｏｌｅｆｉｎｓｕｎｄｅｒｔｈｅｉｎｆｌｕｅｎｃｅｏｆｌｏｗ ｖａｌｅｎｔｔｉｔａｎｉｕｍｒｅａｇｅｎｔｓ ,ｃｏｍｍｏｎｌｙｒｅ ｆｅｒｒｅｄｔｏａｓ“ＭｃＭｕｒｒｙｒｅａｃｔｉｏｎ” ,ｈａｓｂｅｅｎｔｒｅｍｅｎｄｏｕｓｌｙｅｘｐｌｏｉｔｅｄｂｙｃｈｅｍｉｓｔｓｓｉｎｃｅｉｔｓｄｅｂｕｔｉｎｔｈｅｅａｒｌｙ 1970ｓ .1Ａｌｏｔｏｆｏｔｈｅｒｆｕｎｃｔ…     

Single Atom Bi Decorated Copper Alloy Enables C−C Coupling for Electrocatalytic Reduction of CO2 into C2+ Products**

Single atom alloy (SAA) catalysts have been recently explored for promotion of various heterogeneous catalysis, but it remains unexplored for selective electrocatalytic reduction of carbon dioxide (CO₂) into multi-carbon (C₂₊) products involving C−C coupling. Herein we report a single-atomic Bi decorated Cu alloy (denoted as BiCu-SAA) electrocatalyst that could effectively modulate selectivity of CO₂ reduction into C₂₊ products instead of previous C₁ ones. The BiCu-SAA catalyst exhibits remarkably superior selectivity of C₂₊ products with optimal Faradaic efficiency (FE) of 73.4 % compared to the pure copper nanoparticle or Bi nanoparticles-decorated Cu nanocomposites, and its structure and performance can be well maintained at current density of 400 mA cm⁻² under the flow cell system. Based on our in situ characterizations and density functional theory calculations, the BiCu-SAA is found to favor the activation of CO₂ and subsequent C−C coupling during the electrocatalytic reaction, as should be responsible for its extraordinary C₂₊ selectivity.     

The Application of Suzuki Coupling Reaction on the Preparation of Carbosilane Dendrimers with 4-(Naphthalen-1-yl)phenyl Core

The functionalized carbosilane dendrimers can be divided into three categories: surface- functionalization, core-functionalization and focal-point functionalization1-5. The func- tionalized dendrimers can be used as catalyst supporters, medicine control-r…     

Calculating the equilibrium constants of a Sn(II)-H2O-OH− system with allowance for precipitation

A mathematical model is constructed for the Sn(II)-H₂O-OH^? system. The equilibrium constants and regions of precipitation in this system are calculated using four conditions of solution saturation: the solubility product rule, the molecular solubility rule, the solubility rule with respect to the intermediate, and the condition of prior precipitate isolation. The kinetic restraints for equilibration are considered. A mathematical model is constructed for optimizing the synthesis of target compounds.     

An Efficient Synthesis of the α-D-Glucopyranosyl-(1−>2)-α-L-Rhamnopyranosidic Unit

Abstract

The α-D-glucopyranosyl-(1?>2)-L-rhamnopyranosyl sequence is present in some repeating units of bacterial polysaccharides,¹ as those found in the Shigella type or in various Streptococcal strains.     

Silica-Supported Perchloric Acid (HClO4-SiO2): An Efficient Catalyst for the Preparation of β-Amido Carbonyl Compounds Using Multicomponent Reactions

A new, one-pot, efficient, three-component condensation of benzaldehyde derivatives, enolizable ketones, acetyl chloride, and acetonitrile or benzonitrile in the presence of silica-supported perchloric acid as an effective catalyst for the synthesis of β-amido carbonyl compounds is described. The present methodology offers several advantages, such as good yields, short reaction times, and simple workup procedure.     

Efficient C(sp3)−H Carbonylation of Light and Heavy Hydrocarbons with Carbon Monoxide via Hydrogen Atom Transfer Photocatalysis in Flow**

Despite their abundance in organic molecules, considerable limitations still exist in synthetic methods that target the direct C−H functionalization at sp³-hybridized carbon atoms. This is even more the case for light alkanes, which bear some of the strongest C−H bonds known in Nature, requiring extreme activation conditions that are not tolerant to most organic molecules. To bypass these issues, synthetic chemists rely on prefunctionalized alkyl halides or organometallic coupling partners. However, new synthetic methods that target regioselectively C−H bonds in a variety of different organic scaffolds would be of great added value, not only for the late-stage functionalization of biologically active molecules but also for the catalytic upgrading of cheap and abundant hydrocarbon feedstocks. Here, we describe a general, mild and scalable protocol which enables the direct C(sp³)−H carbonylation of saturated hydrocarbons, including natural products and light alkanes, using photocatalytic hydrogen atom transfer (HAT) and gaseous carbon monoxide (CO). Flow technology was deemed crucial to enable high gas-liquid mass transfer rates and fast reaction kinetics, needed to outpace deleterious reaction pathways, but also to leverage a scalable and safe process.     

Photocatalytic hydrogen generation of Pt-Sr(Zr1 − x Y x )O3 − δ -TiO2 heterojunction under the irradiation of simulated sunlight

The Pt-Sr(Zr_{1 − x} Y _x )O_{3 − δ} -TiO₂(Pt-SZYT) heterojunction photocatalysts were prepared by a photodeposition method. The composite particles were characterized by XRD, SEM, UV-Vis DRS, and PL techniques. Photocatalytic hydrogen generation in H₂C₂O₄ aqueous solution under the irradiation of simulated sunlight was used as a probe reaction to evaluate the photocatalytic activity of the photocatalysts. The effects of the content of Pt loading and the concentration of oxalic acid on the photocatalytic activity of the catalyst were discussed. The continuous photocatalytic activity of the Pt-SZYT and the relationship between PL intensity and hydrogen generation were also discussed. The results show that Pt-SZYT catalysts had high photocatalytic activity of hydrogen generation. The content of Pt loading and the concentration of oxalic acid have important influence on the photocatalytic hydrogen generation. The optimal loading content of platinum was 0.90 mass%. Under this condition, the average rate of photocatalytic hydrogen generation was 1.68 mmol·h⁻¹ when the concentration of oxalic acid was 50 mmol·L⁻¹. The higher the photocatalytic activity, the weaker the PL intensity, which was demonstrated by the analysis of PL spectra. __________ Translated from Acta Chimica Sinica, 2008, 61 (in Chinese)     

Theoretical study on the reaction mechanism of NH2(-) with O2 (a1Δg)

A detailed theoretical study of the potential energy surface of poorly understood ion-molecule reaction of NH(2)(-) and O(2) (a(1)Δ(g)) is explored at the density functional theory B3LYP/6-311++G(d,p), ab initio of QCISD/6-311++G(d,p) and CCSD(T)/6-311++G(3df, 2pd) (single-point) theoretical levels for the first time. It is shown that there are six total possible products from P(1) to P(6) on the singlet potential energy surface. Among these, the charge-transfer product P(1) (NH(2) + O(2)(-)) is the most favorable product with predominant abundances, whereas P(4) (NO(-) + H(2)O) and P(2) (HNO + OH(-)) may be the second and third feasible products followed by the almost neglectable P(3) (NO(2)(-) + H(2)), while P(5) (c-NO(2)(-) + H(2)) and P(6) (ONO(-) + H(2)) will not be observed due to their either high barriers or being secondary products. The present theoretical study points out that besides P(1) (NH(2) + O(2)(-)) and P(2) (HNO + OH(-)), P(4) (NO(-) + H(2)O) should be also observed, which is different from the previous experiment study by Anthony Midey et al. in 2008. In addition, almost all of the reaction pathways to products are exothermic and the reaction rate should be very fast since the reaction barriers are very low except for P(5) (c-NO(2)(-) + H(2)) which is in agreement with the measured total reaction rate constant k = 9.0 × 10(-10) cm(3)s(-1) at 300 K in the experiment study. It is expected that the present theoretical study may be helpful for the understanding of the reaction mechanism related to NHX(-), NX(2)(-), PHX(-), and PX(2)(-) (X = H, F, and Cl).     

Two New Catalysts for the Dehydrogenative Coupling Reaction of Carboxylic Acids with Silanes—Convenient Methods for an Atom‐Economical Preparation of Silyl Esters

Tris(triphenylphosphine)cuprous chloride [Cu(PPh₃)₃Cl] has been found to be an efficient catalyst for the dehydrosilylation of carboxylic acids with silanes. In the presence of 4 mol% Cu(PPh₃)₃Cl, dehydrosilylation reactions in acetonitrile afforded the corresponding silyl esters at 80°C in good yields. It was noted that triphenylphosphine itself also functions as an adequate catalyst for the reaction.