A Site Distance Effect Induced by Reactant Molecule Matchup in Single‐Atom Catalysts for Fenton‐like Reactions

Promotion of Single-Electron Transfer by Low-Coordinated Co Single Atoms to Facilitate Advanced Oxidation Processes in Wastewater Treatment

Heterogeneous catalysts are fascinating for advanced oxidation processes (AOPs) in wastewater treatment to reduce cost, metal contamination, and pH operation limitations. However, they usually encounter low catalytic efficiency because of the difficult single-electron-transfer (SET) pathway during AOPs. Herein, an efficient heterogeneous catalyst for AOPs is realized through the rational regulation of N coordination around Co single-atom (SA) centers in favor of SET. As guided by calculations, low N coordination enables a high density of electronic states at the Fermi energy level of SA Co to facilitate SET activation of peroxomonosulfate (PMS). A special oxide-compounding method is further applied to decrease the N coordination of SA Co on the carbon carriers from common Co1-N3/4 to the desired Co1-N2. Co1-N2 shows a delightful activity for AOP degradation of various organic pollutants with kinetic rate and turnover frequency values up to 0.862 min-1 and 389 h-1, respectively, greatly outperforming those of Co1-N3/4. It is also superior in a wide pH operation range and has strong resistance to environmental disturbances. Detailed mechanistic investigations confirm the generation of singlet oxygen (1O2) instead of common radical O species from the SET between PMS and Co1-N2, corroborating the calculated results and accounting for the enhanced AOP activity.

Active Sites for CO2 Hydrogenation to Methanol: Mechanistic Insights and Reaction Control

Catalytic CO2 conversion to methanol is a promising way to extenuate the adverse effects of CO2 emission, global warming and energy shortage. Understanding the fundamental features of CO2 activation and hydrogenation at the molecular level is essential for carbon utilization and sustainable chemical production in the current climate crisis. This review explores the recent advances in understanding the design of catalysts with desired active sites, including single-atom, dual-atom, interface, defects/vacancies and promoters/dopants. We focused on the design of various catalytic systems to enhance their catalytic performances by stabilizing active metal in a catalyst, identifying the unique structure of active species, and engineering coordination environments of active sites. Mechanistic insights provided by advanced operando and in situ spectroscopies were also discussed. Moreover, the review highlights the key factors affecting active sites and reaction mechanisms, such as local environments, oxidation states, and metal-support interactions. By integrating recent advancements and relating knowledge gaps, this review aims to endow an inclusive overview of the field and guide future research toward more efficient and selective catalysts for CO2 hydrogenation to methanol.

A General Metal Ion Recognition Strategy to Mediate Dual-Atomic-Site Catalysts

Heterogeneous dual-atomic-site catalysts (DACs) hold great potential for diverse applications. However, to date, the synthesis of DACs primarily relies on different atoms freely colliding on the support during synthesis, principally leading to low yields. Herein, we report a general metal ion recognition (MIR) strategy for constructing a series of DACs, including but not limited to Fe1Sn1, Fe1Co1, Fe1Ni1, Fe1Cu1, Fe1Mn1, Co1Ni1, Co1Cu1, Co2, and Cu2. This strategy is achieved by coupling target inorganometallic cations and anions as ion pairs, which are sequentially adsorbed onto a nitrogen-doped carbon substrate as the precursor. Taking the oxygen reduction reaction as an example, we demonstrated that the Fe1Sn1-DAC synthesized through this strategy delivers a record peak power density of 1.218 W cm-2 under 2.0 bar H2-O2 conditions and enhanced stability compared to the single-atom-site FeN4. Further study revealed that the superior performance arises from the synergistic effect of Fe1Sn1 dual vicinal sites, which effectively optimizes the adsorption of *OH and alleviates the troublesome Fenton-like reaction.

Multi-channel electron transfer induced by polyvanadate in metal-organic framework for boosted peroxymonosulfate activation

Catalytic peroxymonosulfate (PMS) activation processes don't solely rely on electron transfer from dominant metal centers due to the complicated composition and interface environment of catalysts. Herein the synthesis of a cobalt based metal-organic framework containing polyvanadate [V4O12]4- cluster, Co2(V4O12)(bpy)2 (bpy = 4,4'-bipyridine), is presented. The catalyst demonstrates superior degradation activity toward various micropollutants, with higher highest occupied molecular orbital (HOMO), via nonradical attack. The X-ray absorption spectroscopy and density functional theory (DFT) calculations demonstrate that Co sites act as both PMS trapper and electron donor. In situ spectral characterizations and DFT calculations reveal that the terminal oxygen atoms in the [V4O12]4- electron sponge could interact with the terminal hydrogen atoms in PMS to form hydrogen bonds, promoting the generation of SO5* intermediate via both dynamic pull and direct electron transfer process. Further, Co2(V4O12)(bpy)2 exhibits long-term water purification ability, up to 40 h, towards actual wastewater discharged from an ofloxacin production factory. This work not only presents an efficient catalyst with an electron sponge for water environmental remediation via nonradical pathway, but also provides fundamental insights into the Fenton-like reaction mechanism.

Synergetic Manipulation Mechanism of Single-Atom M-N4 and M-OH (M = Mn, Fe, Co, Ni) Sites for Ozone Activation: Theoretical Prediction and Experimental Verification

Carbon-based single-atom catalysts (SACs) have been gradually introduced in heterogeneous catalytic ozonation (HCO), but the interface mechanism of O3 activation on the catalyst surface is still ambiguous, especially the effect of a surface hydroxyl group (M-OH) at metal sites. Herein, we combined theoretical calculations with experimental verifications to comprehensively investigate the O3 activation mechanisms on a series of conventional SAC structures with N-doped nanocarbon substrates (MN4-NCs, where M = Mn, Fe, Co, Ni). The synergetic manipulation effect of the metal atom and M-OH on O3 activation pathways was paid particular attention. O3 tends to directly interact with the metal atom on MnN4-NC, FeN4-NC, and NiN4-NC catalysts, among which MnN4-NC has the best catalytic activity for its relatively lower activation energy barrier of O3 (0.62 eV) and more active surface-adsorbed oxygen species (Oads). On the CoN4-NC catalyst, direct interaction of O3 with the metal site is energetically infeasible, but O3 can be activated to generate Oads or HO2 species from direct or indirect participation of M-OH sites. The experimental results showed that 90.7 and 82.3% of total organic carbon (TOC) was removed within 40 min during catalytic ozonation of p-hydroxybenzoic acid with MnN4-NC and CoN4-NC catalysts, respectively. Phosphate quenching, catalyst characterization, and EPR measurement further supported the theoretical prediction. This contribution provides fundamental insights into the O3 activation mechanism on SACs, and the methods and ideals could be helpful for future studies of environmental catalysis.

Nicotine-mediated therapy for Parkinson's disease in transgenic Caenorhabditis elegans model

Parkinson's disease resultant in the degeneration of Dopaminergic neurons and accumulation of α-synuclein in the substantia nigra pars compacta. The synthetic therapeutics for Parkinson's disease have moderate symptomatic benefits but cannot prevent or delay disease progression. In this study, nicotine was employed by using transgenic Caenorhabditis elegans Parkinson's disease models to minimize the Parkinson's disease symptoms. The results showed that the nicotine at 100, 150, and 200 μM doses reduced degeneration of Dopaminergic neurons caused by 6-hydroxydopamine (14, 33, and 40%), lowered the aggregative toxicity of α-synuclein by 53, 56, and 78%, respectively. The reduction in food-sensing behavioral disabilities of BZ555 was observed to be 18, 49, and 86%, respectively, with nicotine concentrations of 100 μM, 150 μM, and 200 μM. Additionally, nicotine was found to enhance Daf-16 nuclear translocation by 14, 31, and 49%, and dose-dependently increased SOD-3 expression by 10, 19, and 23%. In summary, the nicotine might a promising therapy option for Parkinson's disease.

Engineering Atomic Ag1-N6 Sites with Enhanced Performance of Eradication Drug-Resistant Bacteria over Visible-Light-Driven Antibacterial Membrane

Utilizing visible light for water disinfection is a more convenient, safe, and practical alternative to ultraviolet-light sterilization. Herein, we developed silver (Ag) single-atom anchored g-C3N4 (P-CN) nanosheets (Ag1/CN) and then utilized a spin-coating method to fabricate the Ag1/CN-based-membrane for effective antibacterial performance in natural water and domestic wastewater. The incorporated Ag single atom formed a Ag1-N6 motif, which increased the charge density around the N atoms, resulting in a built-in electric field ∼17.2 times stronger than that of pure P-CN and optimizing the dynamics of reactive oxygen species (ROS) production. Additionally, the Ag1-N6 motif inhibited the release of Ag ions, ensuring good biocompatibility. Based on the first-principles calculation, the adsorption energy of O2 on the Ag1/CN (-0.32 eV) was lower than that of P-CN (-0.07 eV), indicating that loaded Ag single atom can lower the energy barrier for O2 activation, generating extra *OH radicals that cooperated with *O2- to effectively neutralize bacteria. As a result, the Ag1/CN powder-catalyst with the concentration of 30 ppm demonstrated a 99.9% antibacterial efficiency against drug-resistant bacteria (Escherichia coli, Staphylococcus aureus, kanamycin-resistant Escherichia coli, and methicillin-resistant Staphylococcus aureus) under visible-light irradiation for 4 h. This efficacy was 24.8 times higher than that of the P-CN powder catalyst. Moreover, the Ag1/CN-based-membrane can maintain a 99.9% bactericidal efficiency for natural water and domestic wastewater treatment using a homemade flow device, demonstrating its potential for water disinfection. Notably, the visible-light-driven antibacterial efficiency of the Ag1/CN catalyst outperformed the majority of the reported g-C3N4-based catalysts/membranes.

Nanocurvature-induced field effects enable control over the activity of single-atom electrocatalysts

Tuning interfacial electric fields provides a powerful means to control electrocatalyst activity. Importantly, electric fields can modify adsorbate binding energies based on their polarizability and dipole moment, and hence operate independently of scaling relations that fundamentally limit performance. However, implementation of such a strategy remains challenging because typical methods modify the electric field non-uniformly and affects only a minority of active sites. Here we discover that uniformly tunable electric field modulation can be achieved using a model system of single-atom catalysts (SACs). These consist of M-N4 active sites hosted on a series of spherical carbon supports with varying degrees of nanocurvature. Using in-situ Raman spectroscopy with a Stark shift reporter, we demonstrate that a larger nanocurvature induces a stronger electric field. We show that this strategy is effective over a broad range of SAC systems and electrocatalytic reactions. For instance, Ni SACs with optimized nanocurvature achieved a high CO partial current density of ~400 mA cm-2 at >99% Faradaic efficiency for CO2 reduction in acidic media.

Copper Single-Atom Catalysts-A Rising Star for Energy Conversion and Environmental Purification: Synthesis, Modification, and Advanced Applications

Future renewable energy supply and green, sustainable environmental development rely on various types of catalytic reactions. Copper single-atom catalysts (Cu SACs) are attractive due to their distinctive electronic structure (3d orbitals are not filled with valence electrons), high atomic utilization, and excellent catalytic performance and selectivity. Despite numerous optimization studies are conducted on Cu SACs in terms of energy conversion and environmental purification, the coupling among Cu atoms-support interactions, active sites, and catalytic performance remains unclear, and a systematic review of Cu SACs is lacking. To this end, this work summarizes the recent advances of Cu SACs. The synthesis strategies of Cu SACs, metal-support interactions between Cu single atoms and different supports, modification methods including modification for carriers, coordination environment regulating, site distance effect utilizing, and dual metal active center catalysts constructing, as well as their applications in energy conversion and environmental purification are emphatically introduced. Finally, the opportunities and challenges for the future Cu SACs development are discussed. This review aims to provide insight into Cu SACs and a reference for their optimal design and wide application.

Recent Advances in Laser-Induced Synthesis of MOF Derivatives

Metal-organic frameworks (MOFs) are crystalline materials with permanent pores constructed by the self-assembly of organic ligands and metal clusters through coordination bonds. Due to their diversity and tunability, MOFs are used as precursors to be converted into other types of functional materials by pyrolytic recrystallization. Laser-induced synthesis is proven to be a powerful pyrolytic processing technique with fast and accurate laser irradiation, low loss, high efficiency, selectivity, and programmability, which endow MOF derivatives with new features. Laser-induced MOF derivatives exhibit high versatility in multidisciplinary research fields. In this review, first, the basic principles of laser smelting and the types of materials for laser preparation of MOF derivatives are briefly introduced. Subsequently, it is focused on the peculiarity of the engineering of structural defects and their applications in catalysis, environmental protection, and energy fields. Finally, the challenges and opportunities at the current stage are highlighted with the aim of elucidating the future direction of the rapidly growing field of laser-induced synthesis of MOF derivatives.

Single-atom Mo-Co catalyst with low biotoxicity for sustainable degradation of high-ionization-potential organic pollutants

Single-atom catalysts (SACs) are a promising area in environmental catalysis. We report on a bimetallic Co-Mo SAC that shows excellent performance in activating peroxymonosulfate (PMS) for sustainable degradation of organic pollutants with high ionization potential (IP > 8.5 eV). Density Functional Theory (DFT) calculations and experimental tests demonstrate that the Mo sites in Mo-Co SACs play a critical role in conducting electrons from organic pollutants to Co sites, leading to a 19.4-fold increase in the degradation rate of phenol compared to the CoCl2-PMS group. The bimetallic SACs exhibit excellent catalytic performance even under extreme conditions and show long-term activation in 10-d experiments, efficiently degrading 600 mg/L of phenol. Moreover, the catalyst has negligible toxicity toward MDA-MB-231, Hela, and MCF-7 cells, making it an environmentally friendly option for sustainable water treatment. Our findings have important implications for the design of efficient SACs for environmental remediation and other applications in biology and medicine.

Biodegradable polymeric materials for flexible and degradable electronics

Biodegradable electronics have great potential to reduce the environmental footprint of electronic devices and to avoid secondary removal of implantable health monitors and therapeutic electronics. Benefiting from the intensive innovation on biodegradable nanomaterials, current transient electronics can realize full components’ degradability. However, design of materials with tissue-comparable flexibility, desired dielectric properties, suitable biocompatibility and programmable biodegradability will always be a challenge to explore the subtle trade-offs between these parameters. In this review, we firstly discuss the general chemical structure and degradation behavior of polymeric biodegradable materials that have been widely studied for various applications. Then, specific properties of different degradable polymer materials such as biocompatibility, biodegradability, and flexibility were compared and evaluated for real-life applications. Complex biodegradable electronics and related strategies with enhanced functionality aimed for different components including substrates, insulators, conductors and semiconductors in complex biodegradable electronics are further researched and discussed. Finally, typical applications of biodegradable electronics in sensing, therapeutic drug delivery, energy storage and integrated electronic systems are highlighted. This paper critically reviews the significant progress made in the field and highlights the future prospects.