Cost-effective mitigation of nitrogen pollution from global croplands.

Cropland is a main source of global nitrogen pollution1,2. Mitigating nitrogen pollution from global croplands is a grand challenge because of the nature of non-point-source pollution from millions of farms and the constraints to implementing pollution-reduction measures, such as lack of financial resources and limited nitrogen-management knowledge of farmers3. Here we synthesize 1,521 field observations worldwide and identify 11 key measures that can reduce nitrogen losses from croplands to air and water by 30-70%, while increasing crop yield and nitrogen use efficiency (NUE) by 10-30% and 10-80%, respectively. Overall, adoption of this package of measures on global croplands would allow the production of 17 ± 3 Tg (1012 g) more crop nitrogen (20% increase) with 22 ± 4 Tg less nitrogen fertilizer used (21% reduction) and 26 ± 5 Tg less nitrogen pollution (32% reduction) to the environment for the considered base year of 2015. These changes could gain a global societal benefit of 476 ± 123 billion US dollars (USD) for food supply, human health, ecosystems and climate, with net mitigation costs of only 19 ± 5 billion USD, of which 15 ± 4 billion USD fertilizer saving offsets 44% of the gross mitigation cost. To mitigate nitrogen pollution from croplands in the future, innovative policies such as a nitrogen credit system (NCS) could be implemented to select, incentivize and, where necessary, subsidize the adoption of these measures.

Anchoring Pt Single-Atom Sites on Vacancies of MgO(Al) Nanosheets as Bifunctional Catalysts to Accelerate Hydrogenation-Cyclization Cascade Reactions.

The direct hydrogenation of 2-nitroacylbenzene to 2,1-benzisoxazole presents a significant challenge in the pharmaceutical and fine chemicals industries. In this study, a defect engineering strategy is employed to create bifunctional single-atom catalysts (SACs) by anchoring Pt single atoms onto metal vacancies within MgO(Al) nanosheets. The resultant Pt1/MgO(Al) SAC displays an exceptional catalytic activity and selectivity in the hydrogenation-cyclization of 2-nitroacylbenzene, achieving a 97.5 % yield at complete conversion and a record-breaking turnover frequency of 458.8 h-1 under the mild conditions. The synergistic catalysis between the fully exposed single-atom Pt sites within a unique Pt-O-Mg/Al moiety and the abundant basic sites of the MgO(Al) support is responsible for this outstanding catalytic performance. The current work, therefore, paves the way for developing bifunctional or multifunctional SACs that can enhance efficient organocatalytic conversions.

The Role of Frustrated Lewis Pair in Catalytic Transfer Hydrogenation of Furfural using Nickel Single-Atom Catalysts: A Theoretical Study.

The burgeoning field of frustrated Lewis pair (FLP) heterogeneous catalysts has garnered significant interest in recent years, primarily due to their inherent ability to activate H-source molecules, such as H2, thereby facilitating hydrogenation reactions. However, the application of single metal atom catalysts incorporating FLP sites has been relatively under-explored. In this study, non-precious transition metal atoms were anchored onto a C2N framework with an intrinsic cavity and a defective N-C sheet. Theoretical calculations substantiated energy barriers as low as 0.10 eV for isopropanol activation, thereby positioning these catalysts as highly promising candidates for catalytic transfer hydrogenation of furfural. Electronic structure analyses revealed that the H-O bond breakage in isopropanol molecules was significantly facilitated by the presence of FLP sites within the catalysts. Notably, both Ni-C2N and Ni-N6-C demonstrated exceptional potential as selective catalysts for the hydrogenation of furfural into furfuryl alcohol, exhibiting remarkably low barriers of only 0.65-0.72 eV for the rate-determining steps, which are notably lower than those observed in many traditional catalysts. Theoretical investigations strongly imply that the construction of single atom catalysts with FLP sites could significantly enhance the activity and selectivity for hydrogenation reactions, thus stimulating the experimental synthesis of such catalysts.

Coverage-sensitive mechanism of electrochemical NO reduction on the SrTiO3(001) surface: a DFT investigation.

Due to its adverse environmental and human health hazards, addressing the elimination of nitric oxide (NO) has become a pressing concern for modern society. Currently, electrochemical NO reduction provides a new alternative to traditional selective catalytic reduction technology under mild reaction conditions. However, the complexity and variability of products make the coverage of NO an influencing factor that needs to be investigated. Hence, this study delves into the coverage-sensitive mechanism of electrochemical NO reduction on cost-effective perovskite catalysts, using SrTiO3 as an example, through density functional theory calculations. Phase diagrams analysis reveals that the coverage range from 0.25 to 1.00 monolayer (ML) coverage is favorable for NO adsorption. Gibbs free energy results indicate that the selectivity is significantly influenced by NO coverage. NH3 is likely to be generated at low coverage, while N2O and N2 are more likely to be produced at high coverage through a dimer mechanism. Charge analysis suggests that the charge transfer and Ti-O bond strength between reactants and catalysts are crucial factors. This work not only provides deep insights into coverage-sensitive reaction mechanisms but also is a guideline towards further rational design of high-performance perovskite catalysts.

Seasonal ammonia emissions from an intensive beef cattle feedlot in Victoria Australia.

Ammonia (NH3) emitted from concentrated animal feeding operations can cause environmental and health problems, and indirectly contribute to greenhouse gas emissions. Cattle feedlots are known to be large sources of NH3, but few studies have documented seasonal emissions from Australian feedlots. We conducted two field campaigns to measure NH3 emissions from an intensive beef cattle feedlot in southeast Australia, and these results were combined with previous measurements at the same feedlot to document seasonal variations in emissions and to derive annual feedlot emission factors (EFs). Emission rates were calculated with an inverse dispersion modelling (IDM) technique, based on NH3 concentrations measured at the feedlot with open-path lasers (OPLs). The average area emission rates in spring, summer, autumn and winter were 90.5, 167.4, 96.2 and 86.8 µg NH3 m-2 s-1 from the cattle pens, and 22.5, 18.1, 7.7 and 20.7 µg NH3 m-2 s-1 from the manure stockpile area, respectively. The total per-animal EFs ranged from 126.0 (autumn) to 190.2 g NH3 animal-1 d-1 (summer), representing a loss of 47.5-64.6% of the fed N. Seasonal variations in emissions were related to air temperature. Slight changes in crude protein content of the cattle diet may also have impacted seasonal variability. Taking seasonal variations into consideration, the average feedlot EF was 160.4 g NH3 animal-1 d-1, with 90% of the emissions coming from the cattle pens. Extrapolating the EF to all feedlot cattle in the country, the direct NH3 emissions from Australian feedlots amount to 65.2 Gg NH3 annually, or 3.7% of the national total. Our study benchmarks seasonal and annual EFs and N losses for Australian commercial feedlots, and provides a baseline for extrapolating the impacts of mitigation efforts.

Selective Increase in CO2 Electroreduction to Ethanol Activity at Nanograin-Boundary-Rich Mixed Cu(I)/Cu(0) Sites via Enriching Co-Adsorbed CO and Hydroxyl Species.

Selective producing ethanol from CO2 electroreduction is highly demanded, yet the competing ethylene generation route is commonly more thermodynamically preferred. Herein, we reported an efficient CO2-to-ethanol conversion (53.5 % faradaic efficiency at -0.75 V versus reversible hydrogen electrode (vs. RHE)) over an oxide-derived nanocubic catalyst featured with abundant "embossment-like" structured grain-boundaries. The catalyst also attains a 23.2 % energy efficiency to ethanol within a flow cell reactor. In situ spectroscopy and electrochemical analysis identified that these dualphase Cu(I) and Cu(0) sites stabilized by grain-boundaries are very robust over the operating potential window, which maintains a high concentration of co-adsorbed *CO and hydroxyl (*OH) species. Theoretical calculations revealed that the presence of *OHad not only promote the easier dimerization of *CO to form *OCCO (ΔG~0.20 eV) at low overpotentials but also preferentially favor the key *CHCOH intermediate hydrogenation to *CHCHOH (ethanol pathway) while suppressing its dehydration to *CCH (ethylene pathway), which is believed to determine the remarkable ethanol selectivity. Such imperative intermediates associated with the bifurcation pathway were directly distinguished by isotope labelling in situ infrared spectroscopy. Our work promotes the understanding of bifurcating mechanism of CO2ER-to-hydrocarbons more deeply, providing a feasible strategy for the design of efficient ethanol-targeted catalysts.

Factors of Central Lymph Node Metastasis in Papillary Thyroid Cancer Based on C-TIRADS Analysis.

To study risk factors for central lymph node metastasis (CLNM) in papillary thyroid cancer (PTC) using the Chinese Thyroid Imaging Reporting and Data System (C-TIRADS). We retrospectively analysed patients who underwent PTC surgery and central lymph node dissection at First People's Hospital of Foshan City. The clinical and ultrasonic data of the patients from 1150 cases were analysed by multivariate regression to evaluate the correlation between grayscale ultrasound (US) features, C-TIRADS score, and the classification of thyroid nodules and CLNM of PTCs. The C-TIRADS score was 3.0±1.0 in the CLNM group, which was higher than that in the non-CLNM group (p<0.001). Sex (male) (OR=1.586, 95% CI 1.232-2.042, p<0.001), age (≤45 years) (OR=1.508, 95% CI 1.184-1.919, p=0.001), location of nodes (lower pole) (OR=2.193, 95% CI 1.519-3.166, p<0.001), number (multifocal) (OR=2.204, 95% CI 1.227-2.378, p<0.001), microcalcification (OR=1.610, 95% CI 2.225-4.434, p=0.002), extrathyroidal extension (OR=2.204, 95% CI 1.941-3.843, p<0.001), maximum diameter of nodule (≥20 mm) (OR=3.211, 95% CI 2.337-4.411, p<0.001), and C-TIRADS score (OR=1.356, 95% CI 1.204-1.527, p<0.001) were PTC in independent risk factors for CLNM. The C-TIRADS score of PTC combined with the location, number, size, and ultrasound features of the lesion and the patient's sex and age are important in predicting whether they present with CLNM and provide a reference basis for the clinical formulation of a reasonable surgical treatment plan.

Ligand Conformation Fixation Strategy for Expanding the Structural Diversity of Copper-Tricarboxylate Frameworks and C2H2 Purification Performance Studies.

Structural and functional expansion of metal-organic frameworks (MOFs) is fundamentally important because it not only enriches the structural chemistry of MOFs but also facilitates the full exploration of their application potentials. In this work, by employing a dual-site functionalization strategy to lock the ligand conformation, we designed and synthesized a pair of biphenyl tricarboxylate ligands bearing dimethyl and dimethoxy groups and fabricated their corresponding framework compounds through coordination with copper(II) ions. Compared to the monofunctionalized version, introduction of two side groups can significantly fix the ligand conformation, and as a result, the dual-methoxy compound exhibited a different network structure from the mono-methoxy counterpart. Although only one almost orthogonal conformation was observed for the two ligands, their coordination framework compounds displayed distinct topological structures probably due to different solvothermal conditions. Significantly, with a hierarchical cage-type structure and good hydrostability, the dimethyl compound exhibited promising practical application value for industrially important C2H2 separation and purification, which was comprehensively demonstrated by equilibrium/dynamic adsorption measurements and the corresponding Clausius-Clapeyron/IAST/DFT theoretical analyses.

Boosting CO Catalytic Oxidation Performance via Highly Dispersed Copper Atomic Clusters: Regulated Electron Interaction and Reaction Pathways.

Copper-loaded ceria (Cu/CeO2) catalysts have become promising for the catalytic oxidation of industrial CO emissions. Since their superior redox property mainly arises from the synergistic effect between Cu and the CeO2 support, the dispersion state of Cu species may dominate the catalytic performance of Cu/CeO2 catalysts: the extremely high or low dispersity is disadvantageous for the catalytic performance. The nanoparticle catalysts usually present few contact sites, while the single-atom catalysts tend to be passivated due to their relatively single valence state. To achieve a suitable dispersion state, we synthesized a superior Cu/CeO2 catalyst with Cu atomic clusters, realizing high atomic exposure and unit atomic activity simultaneously via favorable electron interaction and an anchoring effect. The catalyst reaches a 90% CO conversion at 130 °C, comparable to noble-metal catalysts. According to combined in situ spectroscopy and density functional theory calculations, the superior CO oxidation performance of the Cu atomic cluster catalyst results from the joint efforts of effective adsorption of CO at the electrophilic sites, the CO spillover phenomenon, and the efficient bicarbonate pathway triggered by hydroxyl. By providing a superior atomic cluster catalyst and uncovering the catalytic oxidation mechanism of Cu-Ce dual-active sites, our work may enlighten future research on industrial gaseous pollutant removal.

[Two new sesquiterpenes in Qi-nan Aquilariae Lignum Resinatum].

This study aimed to investigate the chemical constituents of supercritical extract from Qi-nan Aquilariae Lignum Resinatum by silica gel column chromatography, thin-layer chromatography, and semi-preparative high-performance liquid chromatography. One new elemane-type and one new eudesmane-type sesquiterpene compounds were isolated from the extract, and their structures were identified by MS, UV, IR, NMR, and ECD spectroscopic techniques, and named aquqinanol C(1) and aquqinanol D(2). Both compounds are novel compounds. The neuroprotective effect of the compounds on CORT-induced PC12 cell damage was determined in vitro. The results showed that compounds 1 and 2 exhibited a certain protective effect against CORT-induced damage in PC12 cells.

Perspective on Defective Semiconductor Heterojunctions for CO2 Photoreduction.

Photocatalytic CO2 reduction to value-added chemicals is a green solution to concurrently address CO2 emission and energy issues, and semiconductor heterojunctions hold great potential to achieve such conversion. However, the photocatalytic performance of the existing heterojunctions is limited by the low interfacial charge transfer efficiency and sluggish surface reaction kinetics. To overcome these obstacles, defect engineering has been applied to heterojunctions to boost CO2 photoreduction in the past 5 years. This perspective summaries the key roles and the related mechanism of various anion vacancies located at the surface, interface, and both surface and interface of heterojunctions in photocatalytic CO2 reduction. Challenges in constructing and characterizating defective heterojunctions as well as in promoting their CO2 photoreduction activity and hydrocarbon selectivity are then outlined. Finally, some solutions to the rational design of defective heterojunctions for efficient and stable CO2 photoreduction are also proposed.

Substituent Engineering-Enabled Structural Rigidification and Performance Improvement for C2/CO2 Separation in Three Isoreticular Coordination Frameworks.

Construction of porous solid materials applied to the adsorptive removal of CO2 from C2 hydrocarbons is highly demanded thanks to the important role C2 hydrocarbons play in the chemical industry but quite challenging owing to the similar physical parameters between C2 hydrocarbons and CO2. In particular, the development of synthetic strategies to simultaneously enhance the uptake capacity and adsorption selectivity is very difficult due to the trade-off effect frequently existing between both of them. In this work, a combination of the dicopper paddlewheel unit and 4-pyridylisophthalate derivatives bearing different substituents afforded an isoreticular family of coordination framework compounds as a platform. Their adsorption properties toward C2 hydrocarbons and CO2 were systematically investigated, and subsequent IAST and density functional theory calculations combined with column breakthrough experiments verified their promising potential for C2/CO2 separations. Furthermore, the substituent engineering endowed the resulting compounds with simultaneous enhancement of uptake capacity and adsorption selectivity and thus better C2/CO2 separation performance compared to their parent compound. The substituent introduction not only mitigated the framework distortion via fixing the ligand conformation for establishment of better permanent porosity required for gas adsorption but also polarized the framework surface for host-guest interaction improvement, thus resulting in enhanced separation performance.

Mechanism of Catalytic Transfer Hydrogenation for Furfural Using Single Ni Atom Catalysts Anchored to Nitrogen-Doped Graphene Sheets.

Catalytic transfer hydrogenation (CTH) of α,ß-unsaturated aldehydes using single metal atom catalysts supported on nitrogen-incorporated graphene sheet (M-Nx-Gr) materials has attracted increasing attention recently, yet the reaction mechanism remains to be explored. Compared to the Ni-N4-Gr model in which the dissociation of isopropanol is highly unfavorable as a result of steric hindrance and inertness of the Ni-N4 site embedded in graphene, the Ni-N3 site in Ni-N3-Gr is more active and facilitates the formation of *H with isopropanol as the H donor, where the dissociation of H from isopropanol with an energy barrier of 0.83 eV is the rate-determining step. An alternative reaction path starts from the coadsorption of isopropanol and furfural molecules at the Ni-N3 site, followed by a direct hydrogen transfer between the two molecules; however, the rate-determining step has a much higher energy barrier of 1.32 eV. Our calculations suggest that the hydrogenation of the aldehyde group is kinetically more favorable than the C═C hydrogenation, revealing the high chemoselectivity of furfural to furfuryl alcohol. Our investigations reveal that the CTH mechanism using the Ni-N3-Gr catalyst is different from that on traditional metal oxides, where the former has only one single active site, while two active sites are required for the latter. The proposed reaction mechanism of CTH for furfural in this study should be helpful to guide the design of single metal atom catalysts with appropriate N coordination for application in chemoselective hydrogenation reactions.

Cadinane-Type Sesquiterpenoids with Cytotoxic Activity from the Infected Stems of the Semi-mangrove Hibiscus tiliaceus.

Eight new cadinane sesquiterpenoids (1-8), along with two known compounds (9 and 10), were isolated from infected stems of the semi-mangrove plant, Hibiscus tiliaceus. The structures of compounds 1-8 were elucidated through the analysis of their 1D and 2D NMR and MS data, and their absolute configurations were determined by comparing their experimental and calculated ECD spectra and by single-crystal X-ray diffraction. The two confused known compounds (9 and 10) were resolved using single-crystal X-ray crystallography. Compounds 1-3 have novel norsesquiterpene carbon skeletons arising from a ring contraction rearrangement. All obtained isolates were evaluated against the HepG2 and Huh7 cell lines, and compounds 1b, 2b, 4, 6, and 8 showed cytotoxic activity toward both cell lines, with IC50 values ranging from 3.5 to 6.8 µM.

Cadinane-type sesquiterpenoid dimeric diastereomers hibisceusones A-C from infected stems of Hibiscus tiliaceus with cytotoxic activity against triple-negative breast cancer cells.

Three new cadinane-type sesquiterpenoid dimeric diastereomers (1-3) named hibisceusones A-C were obtained from the infected stems of Hibiscus tiliaceus. The structures were determined by NMR spectroscopy and MS techniques, and the absolute configurations were assigned by ECD and single-crystal X-ray diffraction techniques. Compounds 1-3 are diastereomers, and contain a 1,4-dioxane ring linearly fused to different cadinane-type polycyclic skeletons. This is the first time that such a structure has been identified in natural products. Compounds 1-3 exhibited cytotoxic activities, and 2 showed a significantly high anti-triple-negative breast cancer (TNBC) effect. The anti-cancer effect of compound 2 was 3-4 fold higher than that of 1 and 3. The anti-cancer effect was generated via the induction of the apoptosis of the MDA-MB-231 cells by inhibiting the PI3Kα pathway.

Theoretical understanding on all-solid frustrated Lewis pair sites of C2N anchored by single metal atom.

The design of all-solid heterogeneous catalysts with frustrated Lewis pairs (FLPs) has attracted much attention recently because of their appealing low dissociation energy for H2 molecules due to which a promotion of hydrogenation reaction is expected. The sterically encumbered Lewis acid (metal site) and base (nitrogen site) in the cavity of single transition metal atom-doped M/C2N sheets make them potential candidates for the design of catalysts with FLPs, while a comprehensive understanding of their intrinsic property and reactivity is still lacking. Calculations show that the complete dissociation of the H2 molecule into two H* states at the N sites requires two steps: heterolytic cleavage of the H2 molecule and the transfer of H* from the metal site to the N site, which are strongly related to the acidity of the metal site. Ni/C2N and Pd/C2N, which outperform the other eight transition metal atom (M) anchored M/C2N candidates, possess low energy barriers for the complete dissociation of H2 molecules, with values of only 0.30 and 0.20 eV, respectively. Furthermore, both Ni/C2N and Pd/C2N catalysts can achieve semi-hydrogenation of C2H2 into C2H4, with overall barriers of 0.81 and 0.75 eV, respectively, which are lower than those reported for many other catalysts. It is speculated that M/C2N catalysts with intrinsic FLPs may also find applications in other important hydrogenation reactions.

Modified lignite and black coal reduce ammonia volatilization from cattle manure.

Modified lignite and black coal (BC) are potential amendments for animal bedding to abate ammonia (NH3) emissions due to their large adsorption capacities for ammoniacal nitrogen (N). However, the ability of modified lignite and BC in reducing NH3 volatilization from livestock manure and the underlying mechanisms remain unknown. The present study has investigated the effect of lignite, modified lignite, BC and modified BC on NH3 volatilization from cattle manure, biological immobilization of manure ammoniacal N and manure properties. Modified lignite and BC reduced the NH3 volatilization from manure by 44 and 36%, respectively, which were comparable with original lignite (43%). The biological immobilization of applied stable isotope labelled 15N in lignite, modified lignite, BC and modified BC amended manures was 15, 18, 11 and 16%, respectively, which were significantly higher than that in unamended manure (4%, P < 0.001). In addition, NH4+-N concentrations of lignite, modified lignite and modified BC amended manures (7.0-7.3 mg g-1) were significantly higher than that of the unamended and original BC amended manures (3.3 and 4.8 mg g-1, respectively, P < 0.001). However, the manure pH in all treatments remained alkaline (pH > 8.2). Our results highlight that the adsorption and immobilization of manure ammoniacal N induced by amendments are the key drivers in reducing NH3 loss from manure, outweighing the pH effect. The findings of this study provide new insights into the mechanisms of coal amendments reducing NH3 loss from animal manure and their potential applications in intensive livestock systems.

Chemical Composition and Potential Properties in Mental Illness (Anxiety, Depression and Insomnia) of Agarwood Essential Oil: A Review.

As a valuable medicinal herb and spice, agarwood is widely used in the fields of daily chemistry, traditional medicine, religion and literary collection. It mainly contains sesquiterpenes and 2-(2-phenylethyl)chromones, which are often used to soothe the body and mind, relieve anxiety, act as an antidepressant and treat insomnia and other mental disorders, presenting a good calming effect. This paper reviews the chemical composition of the essential oils of different sources of agarwood, as well as the progress of research on the sedative and tranquilizing pharmacological activity and mechanism of action of agarwood essential oil (AEO), and then analyzes the current problems of AEO research and its application prospects in the treatment of mental diseases.

The Biosynthesis Related Enzyme, Structure Diversity and Bioactivity Abundance of Indole-Diterpenes: A Review.

Indole diterpenes are a large class of secondary metabolites produced by fungi, possessing a cyclic diterpenoid backbone and an indole moiety. Novel structures and important biological activity have made indole diterpenes one of the focuses of synthetic chemists. Although the discovery, identification, structural diversity, biological activity and especially structure-activity relationship of indole diterpenes have been reported in some papers in recent years, they are absent of a systematic and comprehensive analysis, and there is no elucidation of enzymes related to this kind of natural product. Therefore, it is necessary to summarize the relevant reports to provide new perspectives for the following research. In this review, for the first time, the function of related synthases and the structure-activity relationship of indole diterpenes are expounded, and the recent research advances of them are emphasized.