New well-designed materials are highly demanded with the prospect of versatile properties, offering successful applications as alternates to conventional materials. Major new insights into ...metal-organic self-assembled structures assisting biochemical purposes have recently emerged. Metal-organic polyhedral cages are highlighted as new research materials to be used for therapeutic, sensing and imaging, purposes etc. This tutorial review covers achievements in the biochemical applications of these multinuclear complexes. Examples of their ability to aid the ionic transport, biomolecular sensing, imaging, and drug delivery are presented.
Pincer‐based catalysts possess an exceptional balance of stability versus reactivity, aspects of fundamental interest in catalyst design. This balance has been well‐controlled by systematic ligand ...modifications along with the variation of the metal center. Ruthenium pincer complexes (RPCs), exhibit a versatile chemistry, serve as excellent precursors and find potential applications in many organic transformations. A large number of novel and valuable reactions has been developed using both stoichiometric and catalytic amounts of RPCs. Compared to the traditional ruthenium catalysts, pincer complexes often present high efficiency, selectivity and functional group tolerance. This review highlights different methodologies for the synthesis of RPCs and their catalytic applications for different reactions reported in the last decade. Additionally, the factors affecting the catalytic reactivity of the RPCs and the reaction mechanisms are discussed.
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Two-dimensional (2D) coordination polymers are very interesting materials for their attractive applications. A novel 2D metal-organic framework (MOF) was derived from copper(II) and ...amino benzoic acid under both room temperature and solvothermal reaction conditions using different solvents. From both of the synthesis methods, an identical MOF was crystalized with monoclinic crystal system having P21/c space group. Hirshfeld surface analysis is carried out to explore the non-covalent interactions obtained from single crystal XRD investigation in terms of percentage contribution of each interatomic contact involved in packing of molecules into MOF structure. The microstructure analysis and surface morphology studies revealed the 2D layered regular pattern of rhombus disks of ~5 μm thickness throng together via clustering of these rhombic shaped flakes as flowers (ranging 50–100 μm in size) having uniform elemental composition. This 2D MOF efficiently adsorbed organic dyes (methylene blue, methyl orange, and methyl red) from their aqueous solutions. The 2D copper-carboxylate framework (1.2 g/L) exhibited high adsorption rates for organic dyes (0.15–0.19 mM), and >90% of these dyes could be captured as soon as they are exposed to MOF suspension (1 min) in each case. The dye removal efficiency is credited to synergy among structure, ionic strength, shapes and dimensions of dyes with respect to MOF structure. The microstructure of MOF along with electronic interactions like electrostatic, hydrogen bonding, π-π interactions and coordination to open metal sites, might contribute to the ultrafast dye adsorption process by MOF. The adsorption phenomenon is spontaneous and followed the pseudo-second order kinetic mechanism. DFT calculations revealed important electronic parameters of the dyes and model MOF systems, and novel insights with respect to possible dye-MOF interactions. The MOF remained quite stable during the dye adsorption and was regenerated easily for the successful subsequent use.
•Self-assembled metal-carboxylates of angular/linear di- and tritopic linkers are discussed.•Mixed ligands, interconversion, and postmodifications of nanopolyhedra are addressed.•Crucial synthetic ...protocols for metal to ligand self-organization are summarized.•Potential applications via molecular guest encapsulation mechanism are reported.•These nanocages serve as substrates for extended networks, in sorption, catalytic, and biomedical processes.
Discrete metal-carboxylate cage-like materials are an important class of metal-organic polyhedra. The designs of these self-assemblies in terms of their characteristic polygonal shape, surface area, and related properties are functions of metal centers and carboxylate bridging linkers. Thus, several combinations of different metal ions with angular, linear ditopic, or tritopic carboxylic links can be integrated to map these nanoscale materials, as well as the optional functional groups for the ligands. Synthetic protocols based on variations in the solvent, temperature, and pressure can be employed to achieve metal-carboxylate self-organization. These types of discrete polyhedral nanocages with an internal void are materials with a broad spectrum of potential future uses as substrates for extended networks and highly selective gas sorbents in catalysis and biomedical processes.
•Definitions of pincer ligands and their nomenclature are presented.•Modification of the pincer backbone to control steric and electronic properties.•Design of pincer ligands based on pyridine, ...benzene, etc. for ruthenium pincer complexes (RPCs).•Synthesis of RPCs via direct metallation, C/SiH bond activation, trans-metallation, and trans-cyclometallation.•Key RPC structures affect the catalyst behavior in catalytic hydrogenation reactions.
Active transition–metal complexes based on relatively inexpensive metals are considered to be a desirable method for sustainable human industrial growth. Considering their cost efficiency, ruthenium complexes are gaining increasing attraction, instead of palladium, rhodium, and iridium. Among the ruthenium complexes, ruthenium pincer complexes (RPCs) have received much attention due to their outstanding performance. Various strategies have been developed for pincer ligand design and RPC synthesis, which indicate that ligand design is a key feature of pincer chemistry. In addition, electronic and steric effects, hemilability, non-innocent behavior, and the flexibility of the pincer ligand have significant effects on the catalytic performance of RPCs in hydrogenation and dehydrogenation reactions.
Highly water-soluble cyanocobalamin (also known as vitamin B12) is the most structurally macrocyclic complex comprising cobalt in the center of a corrin ring. Interestingly, it acts as a robust ...electrocatalyst in water oxidation at ∼0.58 V overpotential with a faradaic efficiency of 97.50% under neutral buffered conditions. The catalyst is impressively stable even after long-term bulk electrolysis, and homogeneous in nature, as established by a series of experiments and characterization techniques.
Embedding the fragmented selenium into the micropores of carbon host has been regarded as an effective strategy to change the Li–Se chemistry by a solid–solid mechanism, thereby enabling an excellent ...cycling stability in Li–Se batteries using carbonate electrolyte. However, the effect of spatial confinement by micropores in the electrochemical behavior of carbon/selenium materials remains ambiguous. A comparative study of using both microporous (MiC) and mesoporous carbons (MeC) with narrow pore size distribution as selenium hosts is herein reported. Systematic investigations reveal that the high Se utilization rate and better electrode kinetics of MiC/Se cathode than MeC/Se cathode may originate from both its improved Li+ and electronic conductivities. The small pore size (<1.35 nm) of the carbon matrices not only facilitates the formation of a compact and robust solid‐electrolyte interface (SEI) with low interfacial resistance on cathode, but also alters the insulating nature of Li2Se due to the emergence of itinerant electrons. By comparing the electrochemical behavior of MiC/Se cathode and the matching relationship between the diameter of pores and the dimension of solvent molecules in carbonate, ether, and solvate ionic liquid electrolyte, the key role of SEI film in the operation of C/Se cathode by quasi‐solid‐solid mechanism is also highlighted.
For microporous carbon/Se cathode in carbonate electrolyte, micropores facilitate the formation of thin LiF‐rich solid electrolyte interphase on the C/Se cathode, allowing fast Li+ conduction. The nanoconfinement of micropores can generate the itinerant electrons and alter the insulating nature of Li2Se.
The sluggish kinetics of the oxygen evolution reaction (OER) at the anode severely limit hydrogen production at the cathode in water splitting systems. Although electrocatalytic systems based on ...cheap and earth‐abundant copper catalysts have shown promise for water oxidation under basic conditions, only very few examples with high overpotential can be operated under acidic or neutral conditions, even though hydrogen evolution in the latter case is much easier. This work presents an efficient and robust Cu‐based molecular catalyst, which self‐assembles as a periodic film from its precursors under aqueous conditions on the surface of a glassy carbon electrode. This film catalyzes the OER under neutral conditions with impressively low overpotential. In controlled potential electrolysis, a stable catalytic current of 1.0 mA cm−2 can be achieved at only 2.0 V (vs. RHE) and no significant decrease in the catalytic current is observed even after prolonged bulk electrolysis. The catalyst displays first‐order kinetics and a single site mechanism for water oxidation with a TOF (kcat) of 0.6 s−1. DFT calculations on of the periodic Cu(TCA)2 (HTCA=1‐mesityl‐1H‐1,2,3‐triazole‐4‐carboxylic acid) film reveal that TCA defects within the film create CuI active sites that provide a low overpotential route for OER, which involves CuI, CuII−OH, CuIII=O and CuII−OOH intermediates and is enabled at a potential of 1.54 V (vs. RHE), requiring an overpotential of 0.31 V. This corresponds well with an overpotential of approximately 0.29 V obtained experimentally for the grown catalytic film after 100 CV cycles at pH 6. However, to reach a higher current density of 1 mA cm−2, an overpotential of 0.72 V is required.
Copper can do it: A self‐assembled complex of CuII efficiently catalyzes water oxidation under neutral conditions with a very low overpotential and excellent stability in prolonged electrolysis. Based on DFT calculations, structural defects in the periodic catalyst film could explain the experimentally observed low overpotential of the deposited molecular film in the oxygen evolution reaction.
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•Fuel economy is improved by Al2O3/TiO2 nanolubricants strategy under NEDC.•The vehicle fuel consumption during NEDC was reduced by 4 L/100 km.•The engine brake power and engine ...torque improved during urban and motorway.•Total frictional power losses of gasoline engine were reduced by 5–7%.•The mechanical efficiency of gasoline engine improved in the range 1.7–2.5%.
Energy resources are of strategic interest worldwide. Transportation sector is a principal consumer of different energy resources, therefore reducing the consumption of vital energy resources is critical in automobiles. The friction and wear issues impact the energy efficiency of engines, therefore it is an important development of the lubricant for saving energy. The current study supports that goal. This study deals contribution of Al2O3/TiO2 hybrid nanoparticles as nanolubricants to improve gasoline engine efficiency and fuel economy. The gasoline engine performance characteristics were evaluated experimentally using an AVL dynamometer under different operating conditions including the New European Driving Cycle (NEDC). Additionally, the engine was tested under critical operating conditions (warm-up phase). The results showed that using Al2O3/TiO2 nanolubricants increases the brake power, torque, and mechanical efficiency, while the brake specific fuel consumption (BSFC) reduced owing to the mechanical efficiency of the engine improved by 1.7–2.5%, as compared to the engine oil without nanoparticles. Hence, the vehicle fuel consumption during NEDC could be improved up to 4 L per 100 km in the urban. Furthermore, FESEM, EDS line scanning, XPS, and Raman spectroscopy were conducted to understand the major tribological reasons for improving the engine performance to link tribological tests in the laboratory with actual engine performance. Eventually, the results suggest that nanolubricants provide economical engines with high efficiency that it may be an appropriate direction for vehicle manufacturers and users to suppress the engine fuel cost with engine durability under different operating conditions.
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•The pores in the carbon shells of HCNs play a key role in the Li+ diffusion and Li2Sx confinement.•Simply increasing the shell number in HCNs can not effectively confine the leakage ...of Li2Sx from the S cathode.•Porous 1S-HCNs endow the S cathode with better cycling stability and rate capability than the oligoporous 2S-HCNs and 3S-HCNs do.•After 700 cycles, a capacity of 759 mAh g−1 with 63 % retention is achieved for the S@1S-HCNs cathode at 0.2C.
As a type of sulfur host for lithium-sulfur batteries (LSBs), hollow carbon nanospheres (HCNs) are of particular interest due to their high electrical conductivity, available cavities, and unique morphology. However, there is a lack of in-depth study about the pivotal factors affecting their performance in LSBs. Herein, a series of multi-shelled HCNs have been prepared by a template-free method and the corresponding sulfur cathodes have been systematically investigated. A positive dependence of electrochemical properties on the specific surface area and pore volume of HCNs is confirmed. In case of low porosity of carbon shell, increasing the shell numbers in HCNs could not accelerate the Li+ diffusion and restrict the dissolution of lithium polysulfide in the S@HCNs cathode. As a result, the highly porous 1S-HCNs endow the sulfur cathode with better cycling stability and rate performance than the oligoporous 2S-HCNs and 3S-HCNs do. This work may not only provide a useful reference in the design of novel sulfur hosts but also shed a light on the understanding of the complicated mechanism behind the sulfur redox reactions.
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