The general synthesis and control of the coordination environment of single‐atom catalysts (SACs) remains a great challenge. Herein, a general host–guest cooperative protection strategy has been ...developed to construct SACs by introducing polypyrrole (PPy) into a bimetallic metal–organic framework. As an example, the introduction of Mg2+ in MgNi‐MOF‐74 extends the distance between adjacent Ni atoms; the PPy guests serve as N source to stabilize the isolated Ni atoms during pyrolysis. As a result, a series of single‐atom Ni catalysts (named NiSA‐Nx‐C) with different N coordination numbers have been fabricated by controlling the pyrolysis temperature. Significantly, the NiSA‐N2‐C catalyst, with the lowest N coordination number, achieves high CO Faradaic efficiency (98 %) and turnover frequency (1622 h−1), far superior to those of NiSA‐N3‐C and NiSA‐N4‐C, in electrocatalytic CO2 reduction. Theoretical calculations reveal that the low N coordination number of single‐atom Ni sites in NiSA‐N2‐C is favorable to the formation of COOH* intermediate and thus accounts for its superior activity.
A host–guest cooperative protection strategy has been developed for constructing single‐atom catalysts (SACs), extending the range of available precursors from nitrogenous to non‐nitrogenous MOFs. The obtained Ni‐SACs (NiSA‐Nx‐C; x=2, 3, 4) at different pyrolysis temperatures feature varying nitrogen coordination numbers. The best of these catalysts, NiSA‐N2‐C, shows superior activity and selectivity in CO2 electroreduction.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Covalent organic frameworks (COFs), constructed by organic building blocks through strong covalent bonds, featuring well-defined structures, excellent stability and desired semiconductor-like ...behavior, have been employed for extensive potential applications, especially in photocatalysis. In this review, we summarize the different methods for the synthesis of COFs, such as solvothermal synthesis, microwave synthesis, ionothermal synthesis, room temperature solution synthesis, mechanochemical synthesis and interfacial synthesis firstly. Then, the structural features of COFs such as diversity, tailorability, stability and porosity. Whereafter, the advantages and fundamentals of COFs in photocatalysis are introduced. Furthermore, the photocatalytic applications of COF-based materials toward H2 production, CO2 reduction, organic transformation and pollution degradation are discussed. Particularly, diverse strategies for improving photocatalytic performance and the corresponding structure-activity relationships are highlighted. Finally, the challenges and future prospects for the development of efficient COF-based photocatalysts are briefly indicated.
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•An overview of the introduction of different methods for the synthesis of COFs.•The structural features of COFs including diversity, tailorability, stability and porosity.•The advantages and fundamentals of COFs in photocatalysis.•Photocatalytic applications of COF-based materials in the fields of H2 production, CO2 reduction, organic transformation and pollution degradation.•The challenges and opportunities for the development of COF-based photocatalysts.
Covalent organic frameworks (COFs) are a new class of crystalline porous materials obtained from covalently attached organic building units. By virtue of the unique characteristics such as periodic and well-defined structures, low-density, high surface area, excellent stability as well as desired semiconductor-like behavior, COFs have gained tremendous attention for functional applications in many fields, especially in photocatalysis. In this review, we summarize the different methods for the synthesis of COFs, such as solvothermal synthesis, microwave synthesis, ionothermal synthesis, room temperature solution synthesis, mechanochemical synthesis and interfacial synthesis firstly. Then, the structural features of COFs including diversity, tailorability, stability and porosity are provided. Afterwards, the fundamentals and advantages of COFs for photocatalysis are briefly introduced. Following this, the photocatalytic applications of COF-based materials toward H2 production, CO2 reduction, organic transformation and pollution degradation are discussed. Meanwhile, a series of strategies are highlighted to improve photocatalytic performance for the understanding of the structure-property relationship in this part. Finally, the remaining challenges and prospects on further development of efficient COF-based photocatalysts are indicated.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
While catalysis is highly dependent on the electronic structure of the catalyst, the understanding of catalytic performance affected by electron spin regulation remains challenging and rare. Herein, ...we have developed a facile strategy to the manipulation of the cobalt spin state over covalent organic frameworks (COFs), COF-367-Co, by simply changing the oxidation state of Co centered in the porphyrin. Density functional theory (DFT) calculations together with experimental results confirm that CoII and CoIII are embedded in COF-367 with S = 1/2 and 0 spin ground states, respectively. Remarkably, photocatalytic CO2 reduction results indicate that COF-367-CoIII exhibits favorable activity and significantly enhanced selectivity to HCOOH, accordingly much reduced activity and selectivity to CO and CH4, in sharp contrast to COF-367-CoII. The results highlight that the spin-state transition of cobalt greatly regulates photocatalytic performance. Theoretical calculations further disclose that the presence of CoIII in COF-367-Co is preferable to the formation of HCOOH but detrimental to its further conversion, which clearly accounts for its distinctly different photocatalysis over COF-367-CoII. To the best of our knowledge, this is the first report on regulating photocatalysis by spin state manipulation in COFs.
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IJS, KILJ, NUK, PNG, UL, UM
Aflatoxins and fumonisins (FB) are mycotoxins contaminating a large fraction of the world's food, including maize, cereals, groundnuts and tree nuts. The toxins frequently co-occur in maize. Where ...these commodities are dietary staples, for example, in parts of Africa, Asia and Latin America, the contamination translates to high-level chronic exposure. This is particularly true in subsistence farming communities where regulations to control exposure are either non-existent or practically unenforceable. Aflatoxins are hepatocarcinogenic in humans, particularly in conjunction with chronic hepatitis B virus infection, and cause aflatoxicosis in episodic poisoning outbreaks. In animals, these toxins also impair growth and are immunosuppressive; the latter effects are of increasing interest in human populations. FB have been reported to induce liver and kidney tumours in rodents and are classified as Group 2B ‘possibly carcinogenic to humans’, with ecological studies implying a possible link to increased oesophageal cancer. Recent studies also suggest that the FB may cause neural tube defects in some maize-consuming populations. There is a plausible mechanism for this effect via a disruption of ceramide synthase and sphingolipid biosynthesis. Notwithstanding the need for a better evidence-base on mycotoxins and human health, supported by better biomarkers of exposure and effect in epidemiological studies, the existing data are sufficient to prioritize exposure reduction in vulnerable populations. For both toxins, there are a number of practical primary and secondary prevention strategies which could be beneficial if the political will and financial investment can be applied to what remains a largely and rather shamefully ignored global health issue.
Contamination of agricultural and food products by some fungi species that produce mycotoxins can result in unsafe food and feed. Mycotoxins have been demonstrated to have disease‐causing activities, ...including carcinogenicity, immune toxicity, teratogenicity, neurotoxicity, nephrotoxicity, and hepatotoxicity. Most of mycotoxins are heat stable and cannot be easily destroyed by conventional thermal food processing or domestic cooking methods. Postharvest approaches to prevent growth of mycotoxin‐producing fungi and detoxify mycotoxins from contaminated food are important topics in food safety research. Physical, chemical, and biological methods have been applied to prevent fungal growth or mycotoxin production, or to reduce mycotoxin content in the postharvest period and contribute toward mitigating against the effects of mycotoxins on human health. This literature review aims to evaluate postharvest approaches that have been applied to control both fungi growth and mycotoxin content in food and discuss their potential for upscaling to industrial scale.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Dual‐atom catalysts (DACs) have emerged as efficient electrocatalysts for CO2 reduction owing to the synergistic effect between the binary metal sites. However, rationally modulating the electronic ...structure of DACs to optimize the catalytic performance remains a great challenge. Herein, we report the electronic structure modulation of three Ni2 DACs (namely, Ni2−N7, Ni2−N5C2 and Ni2−N3C4) by the regulation of the coordination environments around the dual‐atom Ni2 centres. As a result, Ni2−N3C4 exhibits significantly improved electrocatalytic activity for CO2 reduction, not only better than the corresponding single‐atom Ni catalyst (Ni−N2C2), but also higher than Ni2−N7 and Ni2−N5C2 DACs. Density functional theory (DFT) calculations revealed that the high electrocatalytic activity of Ni2−N3C4 for CO2 reduction could be attributed to the electronic structure modulation to the Ni centre and the resulted proper binding energies to COOH* and CO* intermediates.
Three Ni2 dual‐atom catalysts (DACs) with electronic structures tailored by the regulation of the coordination environment of Ni atoms, have been prepared for electrocatalytic CO2 reduction. The optimal Ni2−N3C4 exhibits the highest performance for the reduction of CO2 to CO, highlighting the significance of the electronic structure for electrocatalytic CO2 reduction in DACs.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Biomarker-based strategies to assess human exposure to mycotoxins have gained increased acceptance in recent years. In this study, an improved method based on UPLC-MS/MS following 96-well μElution ...solid-phase extraction was developed and validated for the sensitive and high-throughput determination of zearalenone (ZEN) and its five metabolites α-zearalenol (α-ZEL), β-zearalenol (β-ZEL), α-zearalanol (α-ZAL), β-zearalanol (β-ZAL), and zearalanone (ZAN) in human urine samples, using
13
C-ZEN as an internal standard for accurate quantification. Two plates of samples (
n
= 192) could be processed within 2 h, and baseline separation of all the analytes was achieved in a total runtime of 6 min. The proposed method allowed ZEN and its metabolites to be sensitively determined in a high-throughput way for the first time, and with significantly improved efficiency and accuracy with respect to existing methods. The limits of detection (LODs) and limits of quantitation (LOQs) ranged from 0.02 to 0.06 ng mL
−1
and from 0.05 to 0.2 ng mL
−1
, respectively. The recoveries for the spiked samples were from 87.9 to 100%, with relative standard deviations (RSDs) of less than 7%. 301 urine samples collected from healthy volunteers aged 0–84 years in China were analyzed with and without enzyme hydrolysis to determine total and free ZEN biomarkers, respectively. ZEN, ZAN, α-ZEL, and β-ZEL were detected in 71.4% of the samples at levels of 0.02–3.7 ng mL
−1
after enzyme hydrolysis. The estimated mean probable daily intake (PDI) was much lower than the tolerable daily intake (TDI). Adolescents had higher exposure than children, adults, and the elderly.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Exposure to aflatoxin, a mycotoxin common in many foods, has been associated with child growth impairment in sub-Saharan Africa. To improve our understanding of growth impairment in relation to ...aflatoxin and other risk factors, we assessed biospecimens collected in Nepalese children at 15, 24, and 36 months of age for aflatoxin exposure. Children (N = 85) enrolled in the Bhaktapur, Nepal MAL-ED study encompassed the cohort analysed in this study. Exposure was assessed through a plasma biomarker of aflatoxin exposure: the AFB1-lysine adduct. The aflatoxin exposures in the study participants were compared to anthropometrics at each time period (length-for-age LAZ, weight-for-age WAZ, and weight-for-length WLZ z-scores), growth trajectories over time, age, and breastfeeding status. Results demonstrated chronic aflatoxin exposure in this cohort of children, with a geometric mean of 3.62 pg AFB1-lysine/mg albumin. However, the chronic aflatoxin exposure in this cohort was not significantly associated with anthropometric z-scores, growth trajectories, age, or feeding status, based on the available time points to assess aflatoxin exposure. Low mean levels of aflatoxin exposure and infrequent occurrence of stunting, wasting, or underweight z-score values in this cohort are possible contributing factors to a lack of evidence for an association. Further research is needed to examine whether a threshold dose of aflatoxin exists that could induce child growth impairment.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Recent interest in the control of bone metabolism has focused on a specialized subset of CD31
endomucin
vessels, which are reported to couple angiogenesis with osteogenesis. However, the underlying ...mechanisms that link these processes together remain largely undefined. Here we show that the zinc-finger transcription factor ZEB1 is predominantly expressed in CD31
endomucin
endothelium in human and mouse bone. Endothelial cell-specific deletion of ZEB1 in mice impairs CD31
endomucin
vessel formation in the bone, resulting in reduced osteogenesis. Mechanistically, ZEB1 deletion reduces histone acetylation on Dll4 and Notch1 promoters, thereby epigenetically suppressing Notch signaling, a critical pathway that controls bone angiogenesis and osteogenesis. ZEB1 expression in skeletal endothelium declines in osteoporotic mice and humans. Administration of Zeb1-packaged liposomes in osteoporotic mice restores impaired Notch activity in skeletal endothelium, thereby promoting angiogenesis-dependent osteogenesis and ameliorating bone loss. Pharmacological reversal of the low ZEB1/Notch signaling may exert therapeutic benefit in osteoporotic patients by promoting angiogenesis-dependent bone formation.
Catalysts featuring dinuclear metal sites are regarded as superior systems compared with their counterparts with mononuclear metal sites. The dinuclear metal sites in catalysts with appropriate ...spatial separations and geometric configurations can confer the dinuclear metal synergistic catalysis (DMSC) effect, and thus boost the catalytic performance, in particular for reactions involving multiple reactants, intermediates and products. In this review, we summarize the related reports on the design and synthesis of both homogeneous and heterogeneous dinuclear metal catalysts, and their applications in energy conversion reactions, including photo-/electro-catalytic hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), CO
2
reduction reaction (CO
2
RR), and N
2
reduction reaction (N
2
RR). Particularly, we focus on the analysis of the relationship between the catalyst structure and catalytic performances, where the design principles are presented. Finally, we discuss the challenges in the design and preparation of dinuclear metal catalysts with the DMSC effect and present a perspective on the future development of dinuclear metal catalysts in energy conversion. This review aims to comprehensively summarize the up-to-date research progress on the synthesis and energy-related application of dinuclear metal catalysts and provide guidance for designing energy-conversion catalysts with superior performances.
An exclusive review focusing on catalysts exhibiting the dinuclear metal synergistic catalysis (DMSC) effect for energy conversion reactions is presented.
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