Monthly Archives: September 2023

CO2 Hydrogenation to CH3OH over Cu‐Based Catalysts: Primary and Side Reactions

Posted on by
CO2 Hydrogenation to CH3OH over Cu-Based Catalysts: Primary and Side Reactions

This review systematically analyses recent studies on CO2 hydrogenation to methanol with a focus put on primary and secondary reactions. Thermodynamic aspects, active sites and reaction mechanisms are discussed. We also provide personal views on possible developments in this area and recommendations for catalytic tests and their evaluation to properly compare different catalysts.


Abstract

Carbon dioxide (CO2) hydrogenation to methanol (CH3OH) is one of the most promising approaches to provide this platform chemical and to close carbon cycles. In this minireview, we systematically analyze primary and secondary reactions which can take place in this reaction over Cu-based catalysts. In addition to repeatedly discussed reverse water gas shift reaction (RWGS) and CH3OH production directly from CO2, we consider decomposition, dehydration, dehydrogenation, and steam reforming of the desired alcohol. These reactions are usually ignored in the studies dealing with CO2 hydrogenation to CH3OH but can worsen the catalyst efficiency. Apart from the corresponding thermodynamic analysis, proposed reaction mechanisms and active sites are described and discussed. The effects of co-fed water, CH3OH and methyl formate on catalyst performance are critically scrutinized, too. We also provide several criteria for unambiguous comparison of different catalysts in terms of CH3OH selectivity and their activity.

Catalysts Originating from Tailor‐made Metal Ethylene Glycol Carboxylates

Posted on by
Catalysts Originating from Tailor-made Metal Ethylene Glycol Carboxylates

Ethylene glycol metal carboxylates are excellent catalyst precursors for heterogeneous reactions, or can directly be applied in homogeneous catalysis. Applications beyond catalysis are presented.


Abstract

Ethylene glycol metal carboxylates are suited as low-temperature precursors for M and MxOy nanoparticle formation, which are applicable in catalytic heterogeneous reactions including hydrogenations, hydrometalations or C,C cross-couplings. For the synthesis of β-oxo-propyl and enol esters [Ru(CO)2(PPh3)2(O2CR)2] complexes are excellent homogeneous catalysts with high regioselectivities. Additionally, applications of the title complexes beyond catalysis are presented.

Analysis of Dynamical Peculiarities in Nanoalloys at Subsystems Level: Dynamical Degrees of Freedom, Temperature Differences, and the Chameleon Effect

Posted on by
Analysis of Dynamical Peculiarities in Nanoalloys at Subsystems Level: Dynamical Degrees of Freedom, Temperature Differences, and the Chameleon Effect

Vibrational temperatures of pure and mixed 13-atom Ni/Al clusters as a function of the cluster composition and internal energy.


Abstract

A novel analysis of the dynamical behavior of nanoalloy systems, as represented by model Ni/Al 13-atom clusters, over a broad range of energies that cover the stage-wise transition of the systems from their solid-like to liquid-like state is presented. Conceptually, the analysis is rooted in partitioning the systems into judiciously chosen subsystems and characterizing the latter in terms of subsystem-specific dynamical descriptors that include dynamical degrees of freedom, root-mean-square bond-length fluctuation, and element-specific subsystem temperature. The analysis reveals a host of intriguing new peculiarities in the dynamical behavior of the Ni/Al 13-mers, among which are what we call the chameleon effect and the difference in the temperatures of the Ni and Al subsystems at high energies, a difference that strongly depends on the cluster composition and also changes with energy. These do not have an analog in pure Ni13 and Al13 and are explained in terms of the coupled effects of the difference between the masses of the Ni and Al atoms (the mass effect) and of the difference in the anharmonicity of the overall interaction potential as experienced by the Ni and Al subsystems of the clusters (the potential effect).

Conformal Coverage of ZnO Nanowire Arrays by ZnMnO3: Room‐temperature Photodeposition from Aqueous Solution

Posted on by
Conformal Coverage of ZnO Nanowire Arrays by ZnMnO3: Room-temperature Photodeposition from Aqueous Solution

Crystalline–amorphous biphasic ZnMnO3 was photodeposited by a one-step, room-temperature process from an aqueous precursor solution onto ZnO nanowires. The specific morphology of the photodeposit and its homogeneous dispersion at the nanowire surface give rise to an electrode architecture, where ZnMnO3 shells act as an electroactive, pseudocapacitive phase in aqueous electrolytes.


Abstract

Compositionally and structurally complex semiconductor oxide nanostructures gain importance in many energy-related applications. Simple and robust synthesis routes ideally complying with the principles of modern green chemistry are therefore urgently needed. Here we report on the one-step, room-temperature synthesis of a crystalline–amorphous biphasic ternary metal oxide at the ZnO surface using aqueous precursor solutions. More specifically, conformal and porous ZnMnO3 shells are photodeposited from KMnO4 solution onto immobilized ZnO nanowires acting not only as the substrate but also as the Zn precursor. This water-based, low temperature process yields ZnMnO3/ZnO composite electrodes featuring in 1 M Na2SO4 aqueous solution capacitance values of 80–160 F g−1 (as referred to the total mass of the porous film i. e. the electroactive ZnMnO3 phase and the ZnO nanowire array). Our results highlight the suitability of photodeposition as a simple and green route towards complex functional materials.

Efficient Palladium Catalysts: Application and Challenges of Electrocatalytic Hydrodechlorination Technology in Wastewater Treatment

Posted on by
Efficient Palladium Catalysts: Application and Challenges of Electrocatalytic Hydrodechlorination Technology in Wastewater Treatment

This review summarizes the application of palladium catalysts in electrocatalytic hydrodechlorination for the removal of chlorinated organic pollutants. Some strategies for modulating palladium to enhance activity are discussed and future developments in the field are outlined.


Abstract

This review summarizes the research progress of palladium (Pd) catalysts in electrocatalytic hydrodechlorination (ECH) for the removal of chlorinated organic pollutants (COPs). ECH technology is a new type of green water treatment technology without secondary pollution, which has excellent removal effect on COPs. Pd is widely used in the field of ECH due to its excellent catalytic properties. However, the easy deactivation and high price of Pd have limited the application of Pd catalysts in practical wastewater treatment. Researchers have improved the performance of Pd catalysts for ECH by improving the morphological structure (dispersion, particle size, crystalline surface) and electronic states (electron-rich Pd, electron-deficient Pd). It is also found that modulation of the adsorption abilities of Pd catalysts can greatly improve the catalytic activity. The factors affecting the stability of Pd catalysts are also investigated, and the future large-scale mature application of ECH technology is envisioned. The ability to prepare single-atom Pd catalysts in a relatively simple way is a future direction, which will achieve 100 % atom utilization and thus significantly reduce the cost of Pd. This review details the frontier research on Pd catalysts in the field of ECH, which can provide some good strategies for related researchers.

Screening Campaign and Docking Investigations in Identifying New Hit Compounds as Inhibitors of Human Carbonic Anhydrases Expressed In Tumour Cells

Posted on by
Screening Campaign and Docking Investigations in Identifying New Hit Compounds as Inhibitors of Human Carbonic Anhydrases Expressed In Tumour Cells

We explored our in-house collection of sulfonamides to identify new potent hCA IX/XII inhibitors. Docking simulations highlighted the docking poses in catalytic sites of hCA IX and hCA XII cavities. These structural findings may help lead to the successful identification of new sulfonamides as adjuvant agents in cancer management.


Abstract

The tumor-expressed human carbonic anhydrase (hCA) isoforms hCA IX and hCA XII have been extensively studied to develop anticancer agents targeting solid tumors in combined therapy. These CA  isoforms are considered key factors in controlling tumor microenvironment (TME) of cancer lines that develop high metastatic activity. Herein, we report the discovery of potent hCA IX/hCA XII inhibitors that were disclosed through a screening campaign on an in-house collection of arylsulfonamides preliminary tested toward other hCAs. Among them, the N-(4-sulfamoylphenyl)naphthalene-2-carboxamide (12) and N-(4-sulfamoylphenyl)-3,4-dihydroisoquinoline-2(1H)-carbothioamide (15) proved to be the most intriguing hCA IX/hCA XII inhibitors displaying favourable selectivity ratios over widespread hCA I and hCA II isoforms. To explore their binding mode, we conducted docking studies that described the poses of the best inhibitors in the catalytic site of hCA IX and hCA XII, thus suggesting the privileged pattern of interactions. These structural findings might further improve the knowledge for a successful identification of new sulfonamides as adjuvant agents in cancer management.

Graphdiyne‐Based Multiscale Catalysts for Ammonia Synthesis

Posted on by
Graphdiyne-Based Multiscale Catalysts for Ammonia Synthesis

Graphdiyne catalysts for ammonia synthesis! This review highlights the unique structures and properties of graphdiyne, provides a comprehensive update in regard to the synthesis of graphdiyne-based multiscale catalysts and their applications in the synthesis of ammonia, and discusses the challenges and future perspectives relating to graphdiyne.


Abstract

Graphdiyne, a sp/sp2-cohybridized two-dimensional all- carbon material, has many unique and fascinating properties of alkyne-rich structures, large π conjugated system, uniform pores, specific unevenly-distributed surface charge, and incomplete charge transfer properties provide promising potential in practical applications including catalysis, energy conversion and storage, intelligent devices, life science, photoelectric, etc. These superior advantages have made graphdiyne one of the hottest research frontiers of chemistry and materials science and produced a series of original and innovative research results in the fundamental and applied research of carbon materials. In recent years, considerable advances have been made toward the development of graphdiyne-based multiscale catalysts for nitrogen fixation and ammonia synthesis at room temperatures and ambient pressures. This review aims to provide a comprehensive update in regard to the synthesis of graphdiyne-based multiscale catalysts and their applications in the synthesis of ammonia. The unique features of graphdiyne are highlighted throughout the review. Finally, it concludes with the discussion of challenges and future perspectives relating to graphdiyne.

Cu−NHC Complex for Chan‐Evans‐Lam Cross‐Coupling Reactions of N‐Heterocyclic Compounds and Arylboronic Acids

Posted on by
Cu−NHC Complex for Chan-Evans-Lam Cross-Coupling Reactions of N-Heterocyclic Compounds and Arylboronic Acids

An efficient copper(II) N-heterocyclic carbene (NHC) complex catalyzing the Chan–Evans-Lam cross-coupling reaction of N-heterocyclic nucleophiles with arylboronic acid has been explored. This air-stable copper catalyst shows practical robustness that tolerates a diverse array of functional groups on both the N-nucleophile and arylboronic acid coupling partners in C−N bond forming reactions through the CEL reaction.


Abstract

An efficient copper(II) N-heterocyclic carbene (NHC) complex with an NCN coordination mode was optimized to catalyze the Chan–Evans-Lam (CEL) cross-coupling reaction of imidazole and other N-heterocyclic nucleophiles with arylboronic acid. This air-stable copper catalyst shows robust catalytic performance and tolerates a diverse array of functional groups on both the N-nucleophile and arylboronic acid coupling partners in C−N bond forming reactions with up to 95 % yield. Formation of the Cu−NHC complex in situ generated similar catalytic performance for CEL coupling. Alternative metal ions (Mn2+, Fe2+, Co2+, Ni2+, Zn2+, Ru2+, and Pd2+) were also screened in the presence of the NHC precursor as CEL catalysts.

One‐Photon and Two‐Photon Absorption Properties of Multi‐Branched Squaraine Dyes Comprised of Triphenylamine Cores and Ethynylene Linkers

Posted on by
One-Photon and Two-Photon Absorption Properties of Multi-Branched Squaraine Dyes Comprised of Triphenylamine Cores and Ethynylene Linkers

The squaraine chromophores, which have single, two-branched, and three-branched structures with ethynyl-triphenylamine central units, exhibit efficient two-photon absorption (TPA) with a cross section that corresponds to the number of branches present, indicating an additive effect. Among these chromophores, the three-branched dye displays the highest TPA cross section, reaching a maximum value of 4.0×103 GM.


Abstract

We developed multi-branched π-conjugated systems using squaraine dyes with triphenylamine cores connected by ethynylene linkers. We investigated the influence of interbranch coupling between squaraine branches on their one-photon (OPA) and two-photon absorption (TPA) properties. These dyes with triphenylamine components showed a red-shifted one-photon absorption (OPA) compared to the precursor squaraine dyes. Among branched dyes, the lack of apparent splitting or shift in the absorption maxima, even as the absorption intensity increased with the number of chromophores, implies the presence of limited exciton coupling between the squaraine branches. The present squaraine dyes with triphenylamine cores exhibited a moderate TPA compared to the precursor squaraine without the triphenylamine core, due to the extended π-conjugation. Notably, both the 3-branched and 2-branched dyes demonstrated additional enhancement in the TPA response, surpassing that of the monochromophoric counterpart. This resulted in achieving a substantial TPA cross section of up to 3905 GM at 830 nm.

[1,2,4]Triazolo[1,5‐c]pyrimidines as Tools to Investigate A3 Adenosine Receptors in Cancer Cell Lines

Posted on by
[1,2,4]Triazolo[1,5-c]pyrimidines as Tools to Investigate A3 Adenosine Receptors in Cancer Cell Lines

A new series of [1,2,4]triazolo[1,5-c]pyrimidines was investigated at position 2 to obtain potent and selective A3 #adenosine receptor antagonists. #Docking studies were performed to rationalize these results, particularly with respect to selectivity. The best compound in the series was then tested on #cancer cell lines expressing the target receptor and showed an interesting proliferative effect.


Abstract

The A3 adenosine receptor is an interesting target whose role in cancer is controversial. In this work, a structural investigation at the 2-position of the [1,2,4]triazolo[1,5-c]pyrimidine nucleus was performed, finding new potent and selective A3 adenosine receptor antagonists such as the ethyl 2-(4-methoxyphenyl)-5-(methylamino)-[1,2,4]triazolo[1,5-c]pyrimidine-8-carboxylate (20, DZ123) that showed a Ki value of 0.47 nM and an exceptional selectivity profile over the other adenosine receptor subtypes. Computational studies were performed to rationalize the affinity and the selectivity profile of the tested compounds at the A3 adenosine receptor and the A1 and A2A adenosine receptors. Compound 20 was tested on both A3 adenosine receptor positive cell lines (CHO-A3AR transfected, THP1 and HCT16) and on A3 negative cancer cell lines, showing no effect in the latter and a pro-proliferative effect at a low concentration in the former. These interesting results pave the way to further investigation on both the mechanism involved and potential therapeutic applications.