Single-atom catalysts often exhibit unexpected catalytic activity for many important chemical reactions because of their unique electronic and geometric structures with respect to their bulk counterparts. Herein we adopt metal–organic frameworks (MOFs) to assist the preparation of a catalyst containing single Ni sites for efficient electroreduction of CO2. The synthesis is based on ionic exchange between Zn nodes and adsorbed Ni ions within the cavities of the MOF. This single-atom catalyst exhibited an excellent turnover frequency for electroreduction of CO2 (5273 h–1), with a Faradaic efficiency for CO production of over 71.9% and a current density of 10.48 mA cm–2 at an overpotential of 0.89 V. Our findings present some guidelines for the rational design and accurate modulation of nanostructured catalysts at the atomic scale.

Ionic Exchange of Metal–Organic Frameworks to Access Single Nickel Sites for Efficient Electroreduction of CO2

The borrowing hydrogen (BH) principle, also called hydrogen auto-transfer, is a powerful approach which combines transfer hydrogenation (avoiding the direct use of molecular hydrogen) with one or more intermediate reactions to synthesize more complex molecules without the need for tedious separation or isolation processes. The strategy which usually relies on three steps, (i) dehydrogenation, (ii) intermediate reaction, and (iii) hydrogenation, is an excellent and well-recognized process from the synthetic, economic, and environmental point of view. In this context, the objective of the present review is to give a global overview on the topic starting from those contributions published prior to the emergence of the BH concept to the most recent and current research under the term of BH catalysis. Two main subareas of the topic (homogeneous and heterogeneous catalysis) have been identified, from which three subheadings based on the source of the electrophile (alkanes, alcohols, and amines) have been consid...

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Advances in One-Pot Synthesis through Borrowing Hydrogen Catalysis

In this Minireview, the synthesis of amines by the amination of alcohols, by means of the so-called borrowing hydrogen methodology, is presented Compared to other synthetic methodologies for the synthesis of amines, these transformations are highly attractive because often alcohols are readily available starting materials, some of them on a large scale from renewable sources In addition, the amination of alcohols produces water as the only by-product, which makes the process potentially environmentally benign Already today, lower alkyl amines are produced in bulk by the chemical industry with this synthetic method In particular, the recent progress applying organometallic catalysts based on iridium, ruthenium, and other metals will be discussed Notable recent achievements include the conversion of challenging substrates such as diols, the development of recyclable catalysts, milder reaction temperatures, and the direct alkylation of ammonia or its equivalents with alcohols

The Catalytic Amination of Alcohols

Surface Chemistry of Ruthenium Dioxide in Heterogeneous Catalysis and Electrocatalysis: From Fundamental to Applied Research

Transition metal-catalyzed substitution of alcohols by N-nucleophiles (or N-alkylation of amines and related compounds with alcohols) avoids the use of alkylating agents by means of borrowing hydrogen (BH) activation of the alcohol substrates. Water is produced as the only by-product, which makes the “BH” processes atom-economic and environmentally benign. Diverse types of homogeneous organometallic and heterogeneous transition metal catalysts, and substrates such as N-nucleophiles including amines, amides, sulfonamides and ammonia, and various alcohols, can be used for this purpose, demonstrating the promising potential of “BH” processes to replace the procedures using traditional alkylating agents in pharmaceutical and chemical industries. Borrowing hydrogen activation of alcohols for C–N bond formation has recently been paid more and more attention, and a lot of new and novel procedures and examples have been documented. This critical review summarizes the recent advances in “BH” substitution of alcohols by N-nucleophiles since 2009. “Semi-BH” N-alkylation processes with or without an external hydrogen acceptor are also briefly presented. Suitable discussion of the “BH” strategy provides new principles for establishing green processes to replace the relevant traditional synthetic methods for C–N bond formation.

Substitution of alcohols by N-nucleophiles via transition metal-catalyzed dehydrogenation

The N-alkylation of ammonia (or its surrogates, such as urea, NH(4)HCO(3), and (NH(4))(2)CO(3)) and amines with alcohols, including primary and secondary alcohols, was efficiently promoted under anaerobic conditions by the easily prepared and inexpensive supported ruthenium hydroxide catalyst Ru(OH)(x)/TiO(2). Various types of symmetrically and unsymmetrically substituted "tertiary" amines could be synthesized by the N-alkylation of ammonia (or its surrogates) and amines with "primary" alcohols. On the other hand, the N-alkylation of ammonia surrogates (i.e., urea and NH(4)HCO(3)) with "secondary" alcohols selectively produced the corresponding symmetrically substituted "secondary" amines, even in the presence of excess amounts of alcohols, which is likely due to the steric hindrance of the secondary alcohols and/or secondary amines produced. Under aerobic conditions, nitriles could be synthesized directly from alcohols and ammonia surrogates. The observed catalysis for the present N-alkylation reactions was intrinsically heterogeneous, and the retrieved catalyst could be reused without any significant loss of catalytic performance. The present catalytic transformation would proceed through consecutive N-alkylation reactions, in which alcohols act as alkylating reagents. On the basis of deuterium-labeling experiments, the formation of the ruthenium dihydride species is suggested during the N-alkylation reactions.

The “Borrowing Hydrogen Strategy” by Supported Ruthenium Hydroxide Catalysts: Synthetic Scope of Symmetrically and Unsymmetrically Substituted Amines

Aerobic alcohol oxidation catalyzed by supported ruthenium hydroxides

The one-pot synthesis of aldimines from primary alcohols and amines via sequential reactions of alcohol oxidation and dehydrative condensation could efficiently be promoted by supported ruthenium h...

Heterogeneously Catalyzed One-pot Synthesis of Aldimines from Primary Alcohols and Amines by Supported Ruthenium Hydroxides

A stable and highly active oxygen evolution reaction (OER) electrode is the key for fast and robust O2 production, which is one of the essential points for various kinds of energy conversion systems, such as water splitting, lithium-O2 battery and artificial photosynthesis. Here, superaerophobic electrodes with metal@metal-oxide powder catalysts are shown, which demonstrate high and stable OER activity. The active-site-density of metal@metal-oxide catalysts is increased over one order of magnitude than those of pure metal oxides due to the large enhancement of electrical conductivity, revealing the substantial enhancement of electrochemical OER kinetics. Furthermore, the superaerophobic property of electrodes is favorable for fast O2 desorption, which improves electrochemical active surface area (EASA) during OER. The superaerophobic electrode with metal@metal-oxide powder catalysts provides the new insight for increase of active-site-density and EASA simultaneously, which are the key factors to determine the activity of OER electrode.

Superaerophobic Electrode with Metal@Metal‐Oxide Powder Catalyst for Oxygen Evolution Reaction

The N-alkylation of primary amines and ammonia (in situ generated from urea or aqueous ammonia) with alcohols to secondary amines was efficiently promoted by supported copper hydroxide catalysts, C...

Jinling He

Papers

The “Borrowing Hydrogen Strategy” by Supported Ruthenium Hydroxide Catalysts: Synthetic Scope of Symmetrically and Unsymmetrically Substituted Amines

Aerobic alcohol oxidation catalyzed by supported ruthenium hydroxides

Heterogeneously Catalyzed One-pot Synthesis of Aldimines from Primary Alcohols and Amines by Supported Ruthenium Hydroxides

Superaerophobic Electrode with Metal@Metal‐Oxide Powder Catalyst for Oxygen Evolution Reaction

Selective Synthesis of Secondary Amines via N-Alkylation of Primary Amines and Ammonia with Alcohols by Supported Copper Hydroxide Catalysts