Chemistry of Materials
DOI: 10.1021/acs.chemmater.3c02334
Monthly Archives: October 2023
Metal‐free Covalent organic frameworks for Oxygen Reduction Reaction
Oxygen reduction reaction (ORR) is the key reaction in metal air and fuel cells. Among the catalysts towards ORR, carbon-based metal-free catalysts are getting more attention because of their maximum atom utilization, effective active sites and satisfactory catalytic activity and stability. However, the pyrolysis synthesis of these carbons resulted in disordered porosities and uncontrolled catalytic sites, which hindered us to achieve the catalysts’ properties previously, and build the structure–property relationship at molecular level. Covalent organic frameworks (COFs) constructed with designable building blocks have been employed as metal free electrocatalysts towards oxygen reduction reaction (ORR) due to their controlled skeletons, tailored pores size and environments, and well-defined location and kinds of catalytic sites. In this concept article, the development of metal-free COFs for ORR is summarized, and different strategies including skeletons regulation, linkages engineering and edge-sites modulation to improve the catalytic selectivity and activity are discussed. Furthermore, this Concept provides prospective for design and construction high electrocatalysts based on the catalytic COFs.
Synthesis of Organic Optoelectronic Materials Using Direct C‐H Functionalization
Small molecules and polymers with conjugated structures can be used as organic optoelectronic materials. These molecules have conventionally been synthesized by cross-coupling reactions; however, in recent years, direct functionalization of C-H bonds has been used to synthesize organic optoelectronic materials. Representative reactions include direct arylation reactions (C-H/C-X couplings, with X being halogen or pseudo-halogen) and cross-dehydrogenative coupling (C-H/C-H cross-coupling) reactions. Although these reactions are convenient for short-step synthesis, they require regioselectivity in the C-H bonds and suppression of undesired homo-coupling side reactions. This review introduces examples of the synthesis of organic optoelectronic materials using two types of direct C-H functionalization reactions. In addition, we summarize our recent activities in the development of direct C-H functionalization reactions using fluorobenzenes as substrates. This review covers the reaction mechanism and material properties of the resulting products.
Precise Construction of Cu‐Based Catalysts using Surface Molecular Modifiers for Electroreduction of CO2 to Multi‐Carbon Products
Converting CO2 into valuable chemicals has been intensively explored in recent years. Benefited from the substantial cost reduction of renewable electricity, the electrochemical methods have been emerging as a potential means for CO2 capture and conversion. Recently, molecular tuning has been recognized as a powerful technique to modify catalyst’s surface and verified effective in improving CO2RR performance. However, there are few comprehensive and insightful reviews on molecularly modified Cu-based catalysts to precisely modulate the activity and selectivity of C2+ products in CO2 reduction. Herein, the development of CO2RR plausible reaction mechanisms is first introduced. The process and reaction pathways of the carbon-carbon coupling are briefly discussed. Four main aspects of the molecular tuning strategy of the CO2RR are described as the first coordination layer, second coordination layer, outer-layer, and confined effects. The understanding of the improved C2+ performance is demonstrated for molecularly modified Cu-based catalysts. The challenges and perspectives in this field are addressed to further inspire the disclosure of the fundamental understanding in CO2RR, the system optimization, advanced in situ and operando techniques, and integration of CO2 capture and conversion technology with high activity and selectivity for durable applications.
Teaching green chemistry, sustainability ethics, and toxicity using nail polish removers
[ASAP] HeapMS: An Automatic Peak-Picking Pipeline for Targeted Proteomic Data Powered by 2D Heatmap Transformation and Convolutional Neural Networks
Analytical Chemistry
DOI: 10.1021/acs.analchem.3c01011
[ASAP] Structural Evolution of Air-Exposed Layered Oxide Cathodes for Sodium-Ion Batteries: An Example of Ni-doped NaxMnO2
Chemistry of Materials
DOI: 10.1021/acs.chemmater.3c01196
Unraveling propylene oxide formation in alkali metal batteries
The increasing need for electrochemical energy storage drives the development of post-lithium battery systems. Among the most promising battery types are sodium-based battery systems. However, like its lithium predecessor, sodium batteries suffer from various issues like parasitic side reactions, which lead to a loss of active sodium inventory, thus reducing the capacity over time. Some problems in sodium batteries arise from an unstable solid electrolyte interphase (SEI) reducing its protective power. While it is known that the electrolyte affects the SEI structure, the exact formation mechanism of the SEI is not yet fully understood. Here we follow the initial SEI formation on sodium metal submerged in propylene carbonate with and without the electrolyte salt sodium perchlorate. We combine X-ray photoelectron spectroscopy, gas chromatography, and density functional theory to unravel the sudden emergence of propylene oxide after adding sodium perchlorate to the solvent. We identify the formation of a sodium chloride layer as a crucial step in forming propylene oxide by enabling precursors formed from propylene carbonate on the sodium metal surface to undergo a ring-closing reaction. We identify changes in the electrolyte decomposition process, propose a reaction mechanism to form propylene oxide and discuss alternatives based on known synthesis routes.
Mechanochemistry for healthcare: revealing the nitroso derivatives genesis in the solid state
Nitroso derivatives with unique characteristics have been extensively studied in various fields, including biology and clinical research. Even though it has been made an intense investigation of "nitrosable" components in many drugs and commonly consumed nutrients, there is still a need for a higher awareness about their formation and characterization. This study demonstrates how these derivatives can be produced through a mechanochemical procedure under solid-state conditions. The results include synthesizing previously unknown compounds with potential biological and pharmaceutical applications, such as a nitrosamine derived from a Diclofenac-like structure.
The Effect of Pulling and Twisting Forces on Chameleon Sequence Peptides
Chameleon sequences are amino acid sequences found in several distinct configurations in experiment. They challenge our understanding of the link between sequence and structure, and provide insight into structural competition in proteins. Here, we study the energy landscapes for three such sequences, and interrogate how pulling and twisting forces impact the available structural ensembles. Chameleon sequences do not necessarily exhibit multiple structural ensembles on a multifunnel energy landscape when we consider them in isolation. The application of even small forces leads to drastic changes in the energy landscapes. For pulling forces, we observe transitions from helical to extended structures in a very small span of forces. For twisting forces, the picture is much more complex, and highly dependent on the magnitude and handedness of the applied force as well as the reference angle for the twist. Depending on these parameters, more complex and more simplistic energy landscapes are observed alongside more and less diverse structural ensembles. The impact of even small forces is significant, confirming their likely role in folding events. In addition, small forces exerted by the remaining scaffold of a protein may be sufficient to lead to the adoption of a specific structural ensemble by a chameleon sequence.