Cobalt(0)-Catalyzed Isomerization of Allylamines Promoted by Monodentate Benzofuran Phosphines.

Isomerization of C-C double bonds is an efficient tool for converting bulk olefins into high-value compounds. Herein we describe a newly developed homogeneous cobalt-based system which enables the isomerization of allylamines to enamines with similar activity and selectivity to noble metal catalysts. The catalyst activity was bound to the presence of furan-2-yl substituents of the phosphine ligand, while the selectivity was increased with the number of benzofuran-2-yl groups.

Photocatalytic Aqueous Reforming of Methyl Formate.

Green hydrogen is critical to establish a sustainable energy future as it offers a clean, renewable, and a versatile alternative for decarbonizing industries, transportation, and power generation. However, the limitations of current methods significantly restrict the scope and hinder many of the envisioned applications. This study aims to report on the first example of a 3d-metal-based (Cu) heterogeneous photocatalytic system to produce green hydrogen via dehydrogenation of methyl formate (MF), a reaction previously known to require 4d/5d transition metals.

An Atomically Dispersed Photocatalyst for Undirected para-Selective C─H Bond Functionalizations.

Regioselective C─H bond functionalization is pivotal in modern scientific exploration, offering solutions for achieving novel synthetic methodologies and pharmaceutical development. In this aspect, achieving exceptional regioselective functionalization, like para-selective products in electron-poor aromatics, diverges from traditional methods. Leveraging the advantages of atomically dispersed photocatalysts, we designed a robust photocatalyst for an unconventional regioselective aromatic C─H bond functionalization.

Photocatalytic synthesis of ethylene glycol and hydrogen from methyl tert-butyl ether.

In this work, we have developed a green and sustainable strategy for the synthesis of ethylene glycol, which is a highly valuable compound in chemical industry. In contrast to the currently applied energy-intensive process based on petroleum resources, this work demonstrates the photocatalytic pathway of methanol dehydrogenative coupling to produce ethylene glycol, utilizing methyl tert-butyl ether as the substrate to protect the hydroxyl group against oxidation. Photocatalytic tests reveal efficient C-C coupling of methyl tert-butyl ether with Pt/C-TiO(B)-650 catalyst under light irradiation, with the target product 1,2-di-tert-butoxyethane at a selectivity of 67% and a Pt-based turnover frequency of 2754 h.

Photochemical Manganese-Catalyzed [2 + 2 + 2] Cycloaddition Reactions.

We report the cyclotrimerization reactions of triynes using Mn(I) complexes derived from MnBr(CO) and phosphine ligands, such as 1,1-bis(diphenylphosphino)methane (dppm). These reactions are driven by irradiation under mild conditions (30-80 °C) without the need of additional photoinitiators. Our catalytic screening revealed that counteranions and ligands significantly influence the process.

A Transition Metal-Free Approach for the Conversion of Real-Life Cellulose-Based Biomass into Formate.

Formic acid (FA) and its salt are recognized as valuable molecules for various industries such as textiles and pharmaceuticals. Currently, the global demand of FA and its salts stands at 1.137 million metric tons per year, necessitating the development of sustainable methods to meet the future demands.

An Atomically Dispersed Mn Photocatalyst for Vicinal Dichlorination of Nonactivated Alkenes.

A novel Mn-based single-atom photocatalyst is disclosed in this study, designed for the dichlorination of alkenes to achieve vicinal dichlorinated products using -chlorosuccinimide as a mild chlorinating agent, which have widespread applications as pest controlling agents, polymers, flame retardants, and pharmaceuticals. In developing this innovative catalyst, we achieved the atomic dispersion of Mn on aryl-amino-substituted graphitic carbon nitride (CN). This marks the first instance of a heterogeneous version, offering an operationally simple, sustainable, and efficient pathway for dichlorination of alkenes, including drugs, bioactive compounds, and natural products.

A Protocol for Unveiling the Nature of Photocatalytic Hydrogen Evolution Reactions: True Water Splitting or Sacrificial Reagent Acceptorless Dehydrogenation?

Photocatalytic water splitting for hydrogen evolution is a highly topical subject in academic research and a promising approach for sustainable fuel production from solar energy. Due to the mismatched energy diagram of the photosensitizer (especially semiconductor-based materials where band-edge engineering is not trivial) and the redox potential of the half-reactions of water splitting, photocatalytic H generation from water splitting is usually accelerated by the addition of hole scavengers, i.e.

A Covalent Triazine Framework for Photocatalytic Anti-Markovnikov Hydrofunctionalizations.

Porous materials-based heterogeneous photocatalysts, performing selective organic transformations, are increasing the applicability of photocatalytic reactions due to their ability to merge traditional photocatalysis with structured pores densely decorated with catalytic moiety for efficient mass and charge transfer, as well as added recyclability. We herein disclose a porous crystalline covalent triazine framework (CTF)-based heterogeneous photocatalyst that exhibits excellent photoredox properties for different hydrofunctionalization reactions such as hydrocarboxylations, hydroamination and hydroazidations. The high oxidizing property of this CTF enables the activation of styrenes, followed by regioselective C-N and C-O bond formation at ambient conditions.

Unraveling the NH-SCR-DeNO Mechanism of Cu-SSZ-13 Variants by Spectroscopic and Transient Techniques.

Commercial SSZ-13 zeolite with different n(Si)/n(Al) ratios and from different suppliers were subjected to a post-synthetic treatment in order to create mesopores of up to 15 nm. Furthermore, the materials were modified with copper ions and thoroughly physico-chemically characterized. The modified textural properties varied the nature of copper species, and thus, activity in the selective catalytic reduction of NO with ammonia (NH-SCR-DeNO).

A robust Fe-based heterogeneous photocatalyst for the visible-light-mediated selective reduction of an impure CO stream.

The transformation of CO into value-added products from an impure CO stream, such as flue gas or exhaust gas, directly contributes to the principle of carbon capture and utilization (CCU). Thus, we have developed a robust iron-based heterogeneous photocatalyst that can convert the exhaust gas from the car into CO with an exceptional production rate of 145 μmol g h. We characterized this photocatalyst by PXRD, XPS, ssNMR, EXAFS, XANES, HR-TEM, and further provided mechanistic experiments, and multi-scale/level computational studies.

CeO-Supported Single-Atom Cu Catalysts Modified with Fe for RWGS Reaction: Deciphering the Role of Fe in the Reaction Mechanism by In Situ/Operando Spectroscopic Techniques.

Reverse water-gas shift (RWGS) reaction has attracted much attention as a potential approach for CO valorization via the production of synthesis gas, especially over Fe-modified supported Cu catalysts on CeO. However, most studies have focused solely on investigating the RWGS reaction over catalysts with high Cu and Fe loadings, thus leading to an increase in the complexity of the catalytic system and, hence, preventing the gain of any reliable information about the nature of the active sites and reaction mechanism. In this work, a CeO-supported single-atom Cu catalyst modified with iron was synthesized and evaluated for the RWGS reaction.

Red-light-mediated copper-catalyzed photoredox catalysis promotes regioselectivity switch in the difunctionalization of alkenes.

Controlling regioselectivity during difunctionalization of alkenes remains a significant challenge, particularly when the installation of both functional groups involves radical processes. In this aspect, methodologies to install trifluoromethane (-CF) via difunctionalization have been explored, due to the importance of this moiety in the pharmaceutical sectors; however, these existing reports are limited, most of which affording only the corresponding β-trifluoromethylated products. The main reason for this limitation arises from the fact that -CF group served as an initiator in those reactions and predominantly preferred to be installed at the terminal (β) position of an alkene.

Aerobic Oxidative Synthesis of Formamides from Amines and Bioderived Formyl Surrogates.

Herein we present a new strategy for the oxidative synthesis of formamides from various types of amines and bioderived formyl sources (DHA, GLA and GLCA) and molecular oxygen (O) as oxidant on g-CN supported Cu catalysts. Combined characterization data from EPR, XAFS, XRD and XPS revealed the formation of single CuN sites on supported Cu/CN catalysts. EPR spin trapping experiments disclosed ⋅OOH radicals as reactive oxygen species and ⋅NRR radicals being responsible for the initial C-C bond cleavage.

A General Concept for the Electronic and Steric Modification of 1-Metallacyclobuta-2,3-dienes: A Case Study of Group 4 Metallocene Complexes.

The synthesis of group 4 metal 1-metallacyclobuta-2,3-dienes as organometallic analogues of elusive 1,2-cyclobutadiene has so far been limited to SiMe substituted examples. We present the synthesis of two Ph substituted dilithiated ligand precursors for the preparation of four new 1-metallacyclobuta-2,3-dienes [rac-(ebthi)M] (M=Ti, Zr; ebthi=1,2-ethylene-1,10-bis(η-tetrahydroindenyl)). The organolithium compounds [Li(RCPh)] (1 b: R=Ph, 1 c: R=SiMe) as well as the metallacycles of the general formula [rac-(ebthi)M(RCR)] (2 b: M=Ti, R=R=Ph, 2 c: M=Ti, R=Ph, R=SiMe; 3 b: M=Zr, R=R=Ph; 3 c: M=Zr, R=Ph, R=SiMe) were fully characterised.

Aerobic Oxidation of 5-Hydroxymethylfurfural (HMF) in Aqueous Medium over Fe-Doped-Poly(heptazine imide) Photocatalysts: Unveiling the Bad Role of Hydroxyl Radical Generation on the Catalytic Performance.

5-hydroxymethylfurfural (HMF) oxidation in aqueous media using visible photocatalysis is a green and sustainable route for the valorization of lignocellulosic biomass derivatives. Several semiconductors have already been applied for this purpose; however, the use of Poly(heptazine imides), which has high crystallinity and a special cation exchange property that allows the replacement of the cation held between the layers of CN structure by transition metal ions (TM), remains scarce. In this study, PHI(Na) was synthesized using a melamine/NaCl method and used as precursor to prepare metal (Fe, Co, Ni, or Cu)-doped PHI catalysts.

Water-Promoted Carbon-Carbon Bond Cleavage Employing a Reusable Fe Single-Atom Catalyst.

The development of methods for selective cleavage reactions of thermodynamically stable C-C/C=C bonds in a green manner is a challenging research field which is largely unexplored. Herein, we present a heterogeneous Fe-N-C catalyst with highly dispersed iron centers that allows for the oxidative C-C/C=C bond cleavage of amines, secondary alcohols, ketones, and olefins in the presence of air (O ) and water (H O). Mechanistic studies reveal the presence of water to be essential for the performance of the Fe-N-C system, boosting the product yield from <1 % to >90 %.

Experimental Validation and Computational Predictions Join Forces to Map Catalytic C-H Activation in Ferrocene Metalated Porous Organic Polymers.

In recent times, a self-complementary balanced characteristic feature with the combination of both covalent bonds (structural stability) and open metal sites (single-site catalysis) introduced an advanced emerging functional nanoarchitecture termed metalated porous organic polymers (M-POPs). However, the development of M-POPs in view of the current interest in catalysis has been realized still in its infancy and remains a challenge for the years to come. In this work, we built benzothiazole-linked Fe-metalated porous organic polymer () using ferrocene dicarboxaldehyde (), 1,3,5-tris(4-aminophenyl) benzene (), and elemental sulfur (S) via a template-free, multicomponent, cost-effective one-pot synthetic approach.

Unveiling the CO Oxidation Mechanism over a Molecularly Defined Copper Single-Atom Catalyst Supported on a Metal-Organic Framework.

Elucidating the reaction mechanism in heterogeneous catalysis is critically important for catalyst development, yet remains challenging because of the often unclear nature of the active sites. Using a molecularly defined copper single-atom catalyst supported by a UiO-66 metal-organic framework (Cu/UiO-66) allows a detailed mechanistic elucidation of the CO oxidation reaction. Based on a combination of in situ/operando spectroscopies, kinetic measurements including kinetic isotope effects, and density-functional-theory-based calculations, we identified the active site, reaction intermediates, and transition states of the dominant reaction cycle as well as the changes in oxidation/spin state during reaction.

Tailoring Active Cu O/Copper Interface Sites for N-Formylation of Aliphatic Primary Amines with CO /H.

Heterogeneously catalyzed N-formylation of amines to formamide with CO /H is highly attractive for the valorization of CO . However, the relationship of the catalytic performance with the catalyst structure is still elusive. Herein, mixed valence catalysts containing Cu O/Cu interface sites were constructed for this transformation.

Photoexcited cobalt catalysed -selective alkyl Heck reaction.

Herein, we report an intramolecular -selective Heck reaction of iodomethylsilyl ethers of phenols and alkenols. The reaction leads to the formation of seven- and eight-membered siloxycycles in excellent yields, which could be further converted into the corresponding allylic alcohols upon oxidation. Thus, this method could be used for the selective ()-hydroxymethylation of -hydroxystyrenes and alkenols.

Integrating Bifunctionality and Chemical Stability in Covalent Organic Frameworks via One-Pot Multicomponent Reactions for Solar-Driven HO Production.

Multicomponent reactions (MCRs) can be used to introduce different functionalities into highly stable covalent organic frameworks (COFs). In this work, the irreversible three-component Doebner reaction is utilized to synthesize four chemically stable quinoline-4-carboxylic acid DMCR-COFs ( and ) equipped with an acid-base bifunctionality. These DMCR-COFs show superior photocatalytic HO evolution (one of the most important industrial oxidants) compared to the imine COF analogue ().

In Situ-Generated Cu Catalytic System for Oxidative N-Formylation of N-Heterocycles and Acyclic Amines with Methanol.

The development of a sustainable and simple catalytic system for N-formylation of N-heterocycles with methanol by direct coupling remains a challenge, owing to many competing side reactions, given the sensitivity of N-heterocycles to many catalytic oxidation or dehydrogenation systems. This work concerns the development of an in situ-generated Cu catalytic system for oxidative N-formylation of N-heterocycles with methanol that is based on the case study of a more typical 1,2,3,4-tetrahydroquinoline as substrate. Aside from N-heterocycles, some acyclic amines are also transformed into the corresponding N-formamides in moderate yields.

Constitutional isomerism of the linkages in donor-acceptor covalent organic frameworks and its impact on photocatalysis.

When new covalent organic frameworks (COFs) are designed, the main efforts are typically focused on selecting specific building blocks with certain geometries and properties to control the structure and function of the final COFs. The nature of the linkage (imine, boroxine, vinyl, etc.) between these building blocks naturally also defines their properties.