Science China Chemistry最新文献

Identifying the descriptors that control catalytic performance is key to design catalysts with high activity and stability. As indirect descriptors related to catalytic activity, modulating the Pt–Pt interatomic distance and d-band center can effectively enhance the ORR activity. It is well recognized that the Pt–Pt interatomic distance is strongly correlated with the surface strain. Herein, PtMnM/C ternary intermetallics are constructed through partially replacing Mn in PtMn/C binary intermetallics with the other transition metal (M = Fe, Co, Ni, and Cu). The 3d-transition metal doping induces surface strain, and the ORR performance of PtMnM/C exhibits volcano relationship relative to both the Pt–Pt interatomic distance and d-band center. The PtMnCo/C with optimum strain exhibits the highest mass activity (1.06 A mg_Pt⁻¹) at 0.9 V, which is 2.6 and 4.6 times higher than that of PtMn/C and commercial Pt/C catalysts, respectively. In addition, PtMnCo/C shows good durability with only 10 mV half-wave potential decay after 50,000 potential cycles.

The gut microbiota and the associated metabolism play a pivotal role in maintaining human health, yet their assessment is challenging due to their inherent diversity, variety, and complexity. Herein, we developed a multichannel sensor array based on a single fluorescent probe, allowing for rapid and robust profiling gut microbiota and their key metabolites including cysteine (Cys), glutathione (GSH), and homocysteine (Hcy). The assay leverages the single fluorescent probe that is with multiple binding sites and the cross-reactive sensing principle to specifically recognize different biological thiols. By analyzing the pattern of biological thiols, the assay is capable of rapidly identifying six gut-derived bacteria including probiotics, neutral, and pathogenic strains based on fluorescent fingerprints within 5 min, and also discriminating bacteria and their mixtures with different composition. Using the assay that enables the simultaneous measurement of multiple gut-derived bacteria and their metabolites, the designed array achieved an accuracy of 0.99 when discriminating colorectal cancer (CRC) patient feces samples from healthy individuals. Remarkably, the as-prepared sensor array can also be used to identify various stages of CRC. The simplicity, rapidness, and cost-effectiveness of our approach render it a robust platform for the analysis of gut microbiota.

Studying molecular recognition in aqueous environments is crucial for understanding biological processes. Herein, we present a series of N-doped endo-functionalized anthracene-based cavities by introducing inward-directed pyridine units. The subtle modifications can significantly affect the binding properties of these receptors, which is similar to the mutations in biological systems. Combining theoretical calculations and molecular recognition experiments demonstrated that these “mutations” have an impact on the hydrophobicity and charge distribution of the hosts, consequently significantly influencing molecular recognition. This is crucial for understanding the intricate mechanisms of molecular-level interactions in biological receptors.

Rechargeable aqueous zinc batteries (RAZBs) offer a promising solution for large-scale energy storage due to the abundance, low cost, and safety of Zn. However, practical applications are hindered by Zn anode instability, dendrite growth, and hydrogen evolution reactions (HER). Chaotropic Zn(ClO₄)₂ electrolytes are favorable for low-temperature operations but exacerbate these issues due to their high acidity, leading to severe Zn corrosion and layered double hydroxide formation. We propose a biomimetic strategy using methylguanidoacetic acid (creatine) as a low-cost, eco-friendly additive to address these challenges. Creatine acts as a proton pocket to finely tune the pH of acidic Zn(ClO₄)₂ electrolytes for suppressing HER and stabilizing the Zn anode. Furthermore, the formed creatinine cations adsorb on the Zn surface, promoting highly controlled Zn deposition with a preferred (002) orientation. This approach significantly enhances battery cycling performance, with Zn∥Zn cells demonstrating extended cycling stability at both low and high current densities. Zn∥Cu cells exhibited improved Coulombic efficiency over thousands of cycles, indicating highly reversible Zn plating/stripping. Notably, stable cell operations were realized at the temperature as low as −35°C without electrolyte freezing. Our findings highlight the potential of biomimetic proton regulation and interfacial modulation for improving the stability and reversibility of Zn plating/stripping in RAZBs.

Selective modification of peptides has always been a challenging issue. The selective alkylation of peptides can alter the biological activity and physical properties of molecules, and it has gained significant research interest. We herein disclose an intriguing gold-catalyzed alkylation of peptides using bench-stable unactivated alkyl bromides under photoredox catalysis. A wide range of structurally diverse primary, secondary and tertiary alkyl bromides serve as effective coupling partners to precisely connect with the α-C(sp³)–H in glycine residue of peptides. This protocol demonstrates an exceptionally broad scope for alkyl halides and excellent tolerance for a wide range of useful functional groups. A series of relay transformations to construct cyclic peptides, to proceed click reaction and to realize peptide fluorescence labeling further enhance its synthetic practicality. In addition, mechanistic studies and density functional theory (DFT) calculations reveal an inner-sphere and subsequent outer-sphere single electron transfer (SET) mechanism.

An NHC organocatalytic radical aminoacylation of alkenes has been developed by using aldehydes as the acylating reagents and activated aryloxy-amides as the N-radical precursors, providing a new platform for modular access to highly functionalized β-aminoketones. The key to the success of this reaction relies on the single electron transfer (SET) event between the enolates of Breslow intermediates and carefully screened N-radical precursors, followed by a radical addition and radical-radical coupling relay process. The protocol features simple and readily available materials (abundant and feed-stock aldehydes and alkenes), mild reaction conditions (metal-, photo- and oxidant-free, in EA at room temperature), easily removable protecting group for late-stage functionalization.

Cobalamin (Cbl)-dependent radical S-adenosyl-L-methionine (SAM) proteins constitute the largest collection of the radical SAM superfamily that has hundreds of thousands of individual members. Many of these proteins are involved in the biosynthesis of pharmaceutically important natural products to catalyze chemically demanding reactions. In the biosynthetic pathway of chuangxinmycin (CXM), a unique indole alkaloid antibiotic with potent anti-infective activity, functionalization of the characteristic thiopyrano[4,3,2-cd]indole scaffold by regio- and stereoselective C3-methylation is believed to rely on a Cbl-dependent radical process, which, however, remained to be reconstituted biochemically. We here report the dissection of this enzymatic process, which requires the incorporation of Cxm8, a Cbl-dependent radical SAM protein, with Cxm9, a DUF5825 family protein that shares no homology to any proteins of known functions. Cxm8 and Cxm9 function together by forming an unexpected heterodimeric complex that selectively catalyzes C3-methylation of the tricyclic indole-S-hetero ring system in a successive manner, achieving CXM and a recently identified, C3-dimethylated congener. Detailed biochemical characterization, isotope labeling, structural simulation and bioinformatics analysis rationalized the catalysis of the Cxm8/Cxm9 complex and particularly the necessity of the DUF5825 protein for C3-methylase activity. This is the first example that a Cbl-dependent protein acts with a partner to exhibit radical SAM activity.

Electrocatalytic ammonia oxidation reaction (eAOR) is of significance to ammonia fuel economy and the production of valuable N-containing products, such as nitrite, nitrate and hydrazine. The study of well-defined molecular catalysts offers rich insights in terms of the detailed mechanism of ammonia oxidation. This review analyzes the thermodynamics of ammonia oxidation reactions and summarizes the current progress in molecular electrocatalysts in this booming field. We emphasized the factors that influence the selectivity of products and further discussed the challenges in designing efficient catalysts.

Nitrogen-doped carbon materials have been widely used for the constructions of single-atom catalysts, while the effect of different species of doped nitrogen on the catalytic activity of CO₂ electroreduction has rarely been investigated. Here we found that pyrrolic-N coordinated Ni²⁺ catalysts display much higher electrocatalytic CO₂-to-CO activity and selectivity than the corresponding pyridinic-N coordinated low valent Ni⁽⁰⁻⁺²⁾ catalysts, and pyrrolic-N coordinated Ni₂ dual-atoms catalyst of Ni₂/N-CNTs exhibits the best electrocatalytic performance, with over 90% Faradaic efficiencies in a broad potentials from −0.6 to −1.2 V vs. reversible hydrogen electrode, as well as an outstanding CO specific current of 56.2 A/mg_Ni and high turnover frequency of 6.2 × 10⁴ h⁻¹, over 7-times higher than those of pyridinic-N coordinated Ni catalysts. Electrochemical results indicate the weak electron-donor nature of pyrrolic-N facilitates the generation of a reduced active site at low overpotential for boosting CO₂ electroreduction. Density functional theory calculations reveal that the reaction free energy for the *COOH formation on pyrrolic-N coordinated Ni catalysts are lower than those on pyridinic-N coordinated Ni catalysts, and a H₂O-adsorbed Ni₂/N-CNTs displays the optimized reaction free energy for both *COOH formation and CO desorption, which derive the best catalytic performance.

Selective functionaliz0ation of C(sp³)–H bonds is a straightforward and practical method to construct complex molecule skeletons. In this field, direct transformation of unactivated C(sp³)–H bonds into C(sp³)–SCF₃ architectures is still a great challenge. We report a highly selective trifluoromethylthiolation of unactivated aliphatic C(sp³)–H bonds by combination of proton-coupled electron transfer (PCET) and hydrogen atom transfer (HAT) strategy. A wide range of structurally diverse alkyl trifluoromethyl sulfides are obtained. Furthermore, the use of two different photocatalysts can realize an unprecedented trifluoromethylthiolation and amidation cascade of different C(sp³)–H bonds. It can afford a good access to bifunctionalized molecules in synthetically useful yields.