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In this work, we have successfully synthesized a bimetallic (Zinc and Cobalt) Zeolitic Imidazolate Framework (Zn 50 Co 50 -ZIF), a class in a wider microporous Metal-Organic Framework (MOF) family. The synthesized nanostructures maintain both water stability like ZIF-8 (solely Zn containing) and charge transfer electronic band in the visible optical spectrum as ZIF-67 (solely Co containing). Crystal structure from XRD, high resolution transmission electron microscopy (HRTEM) followed by elemental mapping (EDAX) confirm structural stability and omnipresence of the metal atoms (Zn and Co) across the nanomaterial with equal proportion. Existence of charge transfer state consistent with ZIF67 and intact ultrafast excited state dynamics of the imidazolate moiety in both ZIF-8 and ZIF-67, is evidenced from steady state and time resolved optical spectroscopy. The thermal and aqueous stabilities of Zn 50 Co 50 -ZIF are found to be better than ZIF-67 but comparable to ZIF-8 as evidenced by solubility, scanning electron microscopy (SEM) and XRD studies of the material in water. We have evaluated the photoinduced ROS generation by the mixed ZIF employing dichloro-dihydro-fluorescein diacetate (DCFH-DA) assay. We have also explored the potentiality of the synthesized material for the alternate remediation of methicillin resistant Staphylococcus aureus (MRSA) infection through the photoinduced reactive oxygen species (ROS) generation and methylene blue (MB) degradation kinetics.

Small-molecule synthesis usually relies on procedures that are highly customized for each target. A broadly applicable automated process could greatly increase the accessibility of this class of compounds to enable investigations of their practical potential. Here we report the synthesis of 14 distinct classes of small molecules using the same fully automated process. This was achieved by strategically expanding the scope of a building block–based synthesis platform to include even Csp3-rich polycyclic natural product frameworks and discovering a catch-and-release chromatographic purification protocol applicable to all of the corresponding intermediates. With thousands of compatible building blocks already commercially available, many small molecules are now accessible with this platform. More broadly, these findings illuminate an actionable roadmap to a more general and automated approach for small-molecule synthesis.

Covalent organic frameworks (COFs) are crystalline porous polymers constructed from organic building blocks into ordered two- or three-dimensional networks through dynamic covalent bonds. Attributed to their high porosity, well-defined structure, tailored functionality and excellent chemical stability, COFs have been considered ideal sorbents for various separation applications. The synthesis of COFs mainly employs the solvothermal method, which usually requires organic solvents in sealed Pyrex tubes, resulting in unscalable powdery products and environmental pollution that seriously limits their practical applications. Herein, our protocol focuses on an emerging synthesis method for COFs based on organic flux synthesis without adding solvents. The generality of this synthesis protocol has been applied in preparing various types of COFs, including olefin-linked, imide-linked, Schiff-based COFs on both gram and kilogram scales. Furthermore, organic flux synthesis avoids the disadvantages of solvothermal synthesis and enhances the crystallization and porosity of COFs. Typically, COF synthesis takes 3–5 d to complete, and subsequent washing procedures leading to pure COFs need 1 d. The procedure for kilogram-scale production of COFs with commercially available monomers is also provided. The resulting COFs are suitable for separation applications, particularly as adsorbent materials for industrial gas separation and water treatment applications. The protocol is suited for users with prior expertise in the synthesis of inorganic materials and porous organic materials. Key points This protocol describes a flux synthesis approach for two-dimensional covalent organic frameworks (COFs). Compared with other approaches, the method described here does not use solvents, making it environmentally friendly, and is scalable up to the kilogram scale. In addition, high-quality COF monoliths can be generated rather than powdery products, and COFs prepared by this protocol usually possess higher crystallinity and BET surface area than those prepared by traditional solvothermal methods. This protocol describes a flux synthesis approach for two-dimensional covalent organic frameworks. Compared with other approaches, this method does not use solvents, making it environmentally friendly, and is scalable up to the kilogram scale.

Organic chemicals can contribute to local and regional losses of freshwater biodiversity and ecosystem services. However, their overall relevance regarding larger spatial scales remains unknown. Here, we present, to our knowledge, the first risk assessment of organic chemicals on the continental scale comprising 4,000 European monitoring sites. Organic chemicals were likely to exert acute lethal and chronic long-term effects on sensitive fish, invertebrate, or algae species in 14% and 42% of the sites, respectively. Of the 223 chemicals monitored, pesticides, tributyltin, polycyclic aromatic hydrocarbons, and brominated flame retardants were the major contributors to the chemical risk. Their presence was related to agricultural and urban areas in the upstream catchment. The risk of potential acute lethal and chronic long-term effects increased with the number of ecotoxicologically relevant chemicals analyzed at each site. As most monitoring programs considered in this study only included a subset of these chemicals, our assessment likely underestimates the actual risk. Increasing chemical risk was associated with deterioration in the quality status of fish and invertebrate communities. Our results clearly indicate that chemical pollution is a large-scale environmental problem and requires far-reaching, holistic mitigation measures to preserve and restore ecosystem health.

Atmospheric aerosols formed by nucleation of vapors affect radiative forcing and therefore climate. However, the underlying mechanisms of nucleation remain unclear, particularly the involvement of organic compounds. Here, we present high-resolution mass spectra of ion clusters observed during new particle formation experiments performed at the Cosmics Leaving Outdoor Droplets chamber at the European Organization for Nuclear Research. The experiments involved sulfuric acid vapor and different stabilizing species, including ammonia and dimethylamine, as well as oxidation products of pinanediol, a surrogate for organic vapors formed from monoterpenes. A striking resemblance is revealed between the mass spectra from the chamber experiments with oxidized organics and ambient data obtained during new particle formation events at the Hyytiälä boreal forest research station. We observe that large oxidized organic compounds, arising from the oxidation of monoterpenes, cluster directly with single sulfuric acid molecules and then form growing clusters of one to three sulfuric acid molecules plus one to four oxidized organics. Most of these organic compounds retain 10 carbon atoms, and some of them are remarkably highly oxidized (oxygen-to-carbon ratios up to 1.2). The average degree of oxygenation of the organic compounds decreases while the clusters are growing. Our measurements therefore connect oxidized organics directly, and in detail, with the very first steps of new particle formation and their growth between 1 and 2 nm in a controlled environment. Thus, they confirm that oxidized organics are involved in both the formation and growth of particles under ambient conditions.

China’s croplands have experienced drastic changes in management practices, such as fertilization, tillage, and residue treatments, since the 1980s. There is an ongoing debate about the impact of these changes on soil organic carbon (SOC) and its implications. Here we report results from an extensive study that provided direct evidence of cropland SOC sequestration in China. Based on the soil sampling locations recorded by the Second National Soil Survey of China in 1980, we collected 4,060 soil samples in 2011 from 58 counties that represent the typical cropping systems across China. Our results showed that across the country, the average SOC stock in the topsoil (0–20 cm) increased from 28.6 Mg C ha−1 in 1980 to 32.9 Mg C ha−1 in 2011, representing a net increase of 140 kg C ha−1 year−1. However, the SOC change differed among the major agricultural regions: SOC increased in all major agronomic regions except in Northeast China. The SOC sequestration was largely attributed to increased organic inputs driven by economics and policy: while higher root biomass resulting from enhanced crop productivity by chemical fertilizers predominated before 2000, higher residue inputs following the large-scale implementation of crop straw/stover return policy took over thereafter. The SOC change was negatively related to N inputs in East China, suggesting that the excessive N inputs, plus the shallowness of plow layers, may constrain the future C sequestration in Chinese croplands. Our results indicate that cropland SOC sequestration can be achieved through effectively manipulating economic and policy incentives to farmers.

The recent development of a broad range of biocatalysts that can be applied in organic synthesis has brought into focus the need to rethink the way in which organic target molecules might be constructed in the future. To aid synthetic chemists in identifying where biocatalysts might be usefully applied, we propose that guidelines and rules for 'biocatalytic retrosynthesis' be developed and that this new approach be embedded in the future training and education of organic chemists.

Biodegradability testing in soil helps to identify safe synthetic organic chemicals but is still obscured by the formation of soil-bound ‘non-extractable’ residues (NERs). Present-day methodologies using radiocarbon or stable ( 13 C, 15 N) isotope labeling cannot easily differentiate soil-bound parent chemicals or transformation products (xenoNERs) from harmless soil-bound biomolecules of microbial degraders (bioNERs). Hypothesizing a minimal retention of hydrogen in biomolecules, we here apply stable hydrogen isotope – deuterium (D) – labeling to unravel the origin of NERs. Soil biodegradation tests with D- and 13 C-labeled 2,4-D, glyphosate and sulfamethoxazole reveal consistently lower proportions of applied D than 13 C in total NERs and in amino acids, a quantitative biomarker for bioNERs. Soil-bound D thus mostly represents xenoNERs and not bioNERs, enabling an efficient quantification of xenoNERs by just measuring the total bound D. D or tritium (T) labeling could thus improve the value of biodegradability testing results for diverse organic chemicals forming soil-bound residues. Non-extractable residues formation limits biodegradability testing in soil. Here, the authors show that hydrogen isotope tracers are hardly retained in microbial biomass, enabling an efficient distinction between biogenic and xenobiotic residues.

Catalytic systems that allow selective generation of any diastereomer of a reaction product bearing multiple stereocentres through minimal modification of a single catalyst scaffold remain elusive, particularly for carbon–carbon bond formations requiring simultaneous control of multiple selectivity factors. Here, we report a catalyst-directed pinpoint inversion of diastereochemical preference in the 1,6-addition of azlactones to δ-aryl dienyl carbonyl compounds with full control over other selectivities preserved. This rigorous diastereodivergence is enabled by the slight structural adjustment of a chiral iminophosphorane catalyst, providing access to all the stereoisomers with high regio-, distereo- and enantioselectivity. The utility of this method is demonstrated in the facile stereodivergent preparation of densely functionalized proline derivatives. The experimental and computational elucidation of the origin of the diastereodivergence is also reported. For reactions producing numerous chiral centres, accessing all potential stereoisomers is synthetically appealing but difficult. Here, the authors report a stereodivergent 1,6-addition of azlactones where minimal changes to the catalyst structure switches the product selectivity.

Carbon atoms to which four distinct carbon substituents are attached — quaternary carbon stereocentres — are common features of molecules found in nature; in this Review, the authors discuss catalytic enantioselective reactions that have been developed during the past decade for synthesizing organic molecules containing such carbon atoms. Synthesis of quaternary carbon stereocentres Carbon atoms with four distinct carbon substituents attached — known as quaternary stereocentres — are found in many biologically active natural products, such as cortisone and morphine. This important structural motif has proved a challenge to synthetic chemists and until recently there were few methods available for its construction. Here Kyle Quasdorf and Larry Overman discuss the catalytic enantioselective reactions that have been developed during the past decade for synthesizing organic molecules containing quaternary stereocentres. The methods now available remove much of the previous barrier to incorporating quaternary stereocentres in organic molecules for use in medicine, agriculture and other areas. Quaternary carbon stereocentres—carbon atoms to which four distinct carbon substituents are attached—are common features of molecules found in nature. However, before recent advances in chemical catalysis, there were few methods of constructing single stereoisomers of this important structural motif. Here we discuss the many catalytic enantioselective reactions developed during the past decade for the synthesis of single stereoisomers of such organic molecules. This progress now makes it possible to incorporate quaternary stereocentres selectively in many organic molecules that are useful in medicine, agriculture and potentially other areas such as flavouring, fragrances and materials.