Core-Shell Covalently Linked Graphitic Carbon Nitride-Melamine-Resorcinol-Formaldehyde Microsphere Polymers for Efficient Photocatalytic CO2 Reduction to Methanol.

Photocatalytic reduction of CO2 with light and H2O to form CH3OH is a promising route to mitigate carbon emissions and climate changes. Although semiconducting metal oxides are potential photocatalysts for this reaction, low photon efficiency and leaching of environmentally unfriendly toxic metals limit their applicability. Here, we report metal-free, core-shell photocatalysts consisting of graphitic carbon nitride (g-C3N4, CN) covalently linked to melamine-resorcinol-formaldehyde (MRF) microsphere polymers for this reaction. Covalent linkage enabled efficient separation of photo-generated carriers and photocatalysis. Using 100 mg of a photocatalyst containing 15 wt % CN, a CH3OH yield of 0.99 µmol·h-1 was achieved at a reaction temperature of 80 °C and 0.5 MPa with external quantum efficiencies ranging from 5.5% at 380 nm to 1.7% at 550 nm. The yield was about 20 and 10 times higher than that of its components CN and MRF, respectively. Characterization with X-ray photoelectron spectroscopy, transmission electron microscopy, and bulk and surface elemental analyses supported the formation of a core-shell structure and the charge transfer in the C-N bond at the CN-MRF interface between the methoxy group in the 2,4-dihydroxylmethyl-1,3-diphenol part of MRF and the terminal amino groups in CN. This enhanced ligand-to-ligand charge transfer resulted in 67% of the photo-excited internal charge transferred from CN to the hydroxymethylamino group in MRF, whose amino group was the catalytic site for the CO2 photocatalytic reduction to CH3OH. This study provides a series of new metal-free photocatalyst designs and insights into the molecular-level structure-mediated photocatalytic response.

Synthesis of methanol from CO2 hydrogenation promoted by dissociative adsorption of hydrogen on a Ga3Ni5(221) surface.

Catalytic carbon dioxide (CO2) hydrogenation to liquid fuels including methanol (CH3OH) has attracted great attention in recent years. In this work, density functional theory (DFT) calculations have been employed to study the reaction mechanisms of CO2 hydrogenation to CH3OH on Ga3Ni5(221) surfaces. The results show that all intermediates except for the O atom prefer to adsorb on Ni sites, and dissociative adsorption of hydrogen (H2) on the Ga3Ni5(221) surface is almost barrierless and highly exothermic, favoring CO2 hydrogenation. Moreover, the presence of Ga indeed enhances the dissociative adsorption of H2, and this is verified by the projected density of states (PDOS) analysis. Importantly, three possible reaction pathways based on formate (HCOO) and hydrocarboxyl (COOH) formations and reverse water gas shift (rWGS) with carbon monoxide (CO) hydrogenation have been discussed. It is found that CO2 reduction to CH3OH in these pathways prefers to occur entirely via the Langmuir-Hinshelwood (L-H) mechanism. COOH generation is the most favorable pathway because the HCOO and rWGS with CO hydrogenation pathways have high energy barriers and the resulting HCOOH intermediate in the HCOO pathway is unstable. In the COOH reaction pathway, CO2 is firstly hydrogenated to trans-COOH, followed by the formation of COH via three isomers of COHOH, its hydrogenation to trans-HCOH, and then the production of CH3OH via a CH2OH intermediate.

Two-dimensional and Three-dimensional quantitative structure-activity relationship models for the degradation of organophosphate flame retardants during supercritical Water oxidation.

Organophosphate flame retardants (OPFRs) have been increasingly utilized as flame retardants in various fields due to the phasing out of polybrominated diphenyl ethers. To achieve a better understanding of the degradation of OPFRs undergoing supercritical water oxidation (SCWO) process, two-dimensional and three-dimensional quantitative structure-activity relationship (2D-QSAR and 3D-QSAR) models were established to investigate the factors influencing the total carbon degradation rates (kTOC). Results of the QSAR models demonstrated reliable results to estimate the kTOC values, but varied in the influencing factors. Two distinct degradation mechanisms were subsequently proposed based on the distribution of LUMO in molecules for the 2D-QSAR model. CoMFA and CoMSIA methods were applied to develop the 3D-QSAR models. Steric fields were observed to influence kTOC values more than electrostatic fields in the CoMFA model with the contribution rates of 87.2% and 12.8%, respectively. In the CoMSIA model, influence on kTOC values varies between different types of fields with the hydrophobic field being the most influential at 62.1%, followed by the steric field at 25.7% and then the electrostatic field at 10.8%. Results from this study generated critical knowledge of influencing factors on OPFRs degradation and yielded theoretical basis for estimating removal behaviors of OPFRs undergoing SCWO process.

A new and different insight into the promotion mechanisms of Ga for the hydrogenation of carbon dioxide to methanol over a Ga-doped Ni(211) bimetallic catalyst.

The hydrogenation of CO2 to CH3OH is one of the most promising technologies for the utilization of captured CO2 in the future. Nano Ni-Ga bimetallic catalysts have been proven to be excellent catalysts in the hydrogenation of CO2 to CH3OH. To investigate the promotion mechanisms of Ga for the hydrogenation of CO2 to CH3OH over Ga-doped Ni catalysts and the wide application of these promotion mechanisms in other catalysts and reactions, herein, density functional theory (DFT) was employed. The reaction mechanisms and the properties of Ni(211) and Ga-Ni(211) surfaces were comparatively studied. The results show that the Ni sites on both the Ni(211) and the Ga-Ni(211) surfaces are active sites, and the most stable structures of the intermediates are similar. Moreover, the Ga-Ni(211) surface is more favorable for the hydrogenation of CO2, whereas Ni(211) is more favorable for the dissociation of CO2. The activation barrier of the rate-limiting step in the CH3OH formation pathway on Ni(211) is 0.54 eV higher than that on Ga-Ni(211). According to the analyses of the projected density of states (PDOS) and Hirshfeld charge transfer, the addition of Ga atoms demonstrates the reactivity of the Ga-doped Ni(211) surfaces. Most importantly, the replacement of some secondary active sites of Ni atoms with the non-active Ga atoms may lower the activities of the secondary active sites and strengthen the activities of the active sites at the step edge. These results provide a new perspective for the reaction mechanism of the hydrogenation of CO2 to CH3OH over the state-of-the-art Ga-doped catalysts.

Antioxidative and Immunomodulatory Activities of the Exopolysaccharides from Submerged Culture of Hen of the Woods or Maitake Culinary-Medicinal Mushroom, Grifola frondosa (Agaricomycetes) by Addition of Rhizoma gastrodiae Extract and Its Main Components.

Grifola frondosa (hen of the woods or maitake) is a famous culinary-medicinal mushroom, and its exopolysaccharides (EPSs) have biological activities with or without supplementation with exogenous additives. In this study, a Rhizoma gastrodiae extract was added to a G. frondosa fermentation system. P-hydroxylbenzaldehyde (HBA), the main product of R. gastrodiae, had the highest utilization rate in the fermentation process (42%). In addition, the EPSs of G. frondosa after addition of R. gastrodiae extract (REPS), of HBA (HEPS), or of a standard solution according to the main component ratio of R. gastrodiae extract (CEPS) were obtained. We then determined the antioxidant and immunomodulatory activities of EPS, REPS, HEPS, and CEPS. Overall, REPS showed the highest antioxidant activities compared with EPS and HEPS (P < 0.05) but similar to that of CEPS (P > 0.05). The half-inhibitory concentration (ED50) values of REPS (< 4 mg/mL) were lower than those of EPS, HEPS, and CEPS. Moreover, REPS was better able to stimulate phagocytosis and nitric oxide production of RAW 264.7 macrophages than were the others, without a significant difference from CEPS (P > 0.05). An interesting and important finding is that a R. gastrodiae extract can increase antioxidant and immunomodulatory activities of EPS preparations from G. frondosa, and the standard solution of the main components of the R. gastrodiae extract may be better for simulating fermentation performed by G. frondosa and biological activities of its major products.

Nitrogen transformation of 41 organic compounds during SCWO: A study on TN degradation rate, N-containing species distribution and molecular characteristics.

Supercritical water oxidation (SCWO) of 41 N-containing compounds was examined under a stable temperature and pressure of 450 °C and 24 MPa, respectively, reaction time ranged from 0.5 to 6 min with 500% excess oxygen, resulted in the degradation rate constants of total organic carbon (kTOC) and total nitrogen (kTN) were 0.162-3.693 and 0.065-0.416 min-1, respectively. The N-containing products were primary N2, ammonium and nitrate. As for amino-group compounds, the main product was ammonia, while for nitro-group compounds, nitrate was the predominant. In terms of diazo and N-heterocyclic group compounds, the main products generally were nitrate and ammonium, respectively. Interestingly, 2-, 3- and 4-nitroaniline, containing both of nitro and amino group, would directly decompose into N2. The reaction pathways of acid orange 74 was proposed based on Fukui indices, which generally included denitrification, ring-open and mineralization. Density functional theory (DFT) method was applied to calculate the quantum properties of the 41 N-containing compounds in order to further examine the relationship between TN removal and molecular structural characteristics. The correlation result showed that among all the 17 molecular characteristics, F(+)n, F(-)n, F(0)n, and EHOMO achieved high correlation coefficients.

QSAR models for degradation of organic pollutants in ozonation process under acidic condition.

Although some researches about the degradation of organic pollutants have been carried out during recent years, reaction rate constants are available only for homologue compounds with similar structures or components. Therefore, it is of great significance to find a universal relationship between reaction rate and certain parameters of several diverse organic pollutants. In this study, removal ratio and kinetics of 33 kinds of organic substances were investigated by ozonation process, including azo dyes, heterocyclic compounds, ionic compounds and so on. Most quantum chemical parameters were conducted by using Gaussian 09 at the DFT B3LYP/6-311G level, including µ, q H(+), q(C)minq(C)max, ELUMO and EHOMO. Other descriptors, bond order (BO) as well as Fukui indices (f(+), f(-) and f(0)), were calculated by Material Studio 6.1 at Dmol(3)/GGA-BLYP/DNP(3.5) basis for each organic compound. The recommended model for predicting rate constants was lnk'=1.978-95.484f(0)x-3.350q(C)min+38.221f(+)x, which had the squared regression coefficient R(2)=0.763 and standard deviation SD=0.716. The results of t test and the Fisher test suggested that the model exhibited optimum stability. Also, the model was validated by internal and external validations. Recommended QSAR model showed that the highest f(0) value of main-chain carbons (f(0)x) is more closely related to lnk' than other quantum descriptors.

RNA-Seq Based De Novo Transcriptome Assembly and Gene Discovery of Cistanche deserticola Fleshy Stem.

BACKGROUNDS: Cistanche deserticola is a completely non-photosynthetic parasitic plant with great medicinal value and mainly distributed in desert of Northwest China. Its dried fleshy stem is a crucial tonic in traditional Chinese medicine with roles of mainly improving male sexual function and strengthening immunity, but few mechanistic studies have been conducted partly due to the lack of genomic and transcriptomic resources. RESULTS: In this study, we performed deep transcriptome sequencing in fleshy stem of C. deserticola, and about 80 million reads were generated using Illumina pair-end sequencing on HiSeq2000 platform. Using trinity assembler, we obtained 95,787 transcript sequences with transcript lengths ranging from 200 bp to 15,698 bp, having an average length of 950 bases and the N50 length of 1,519 bases. 63,957 transcripts were identified actively expressed with FPKM ≥ 0.5, in which 30,098 transcripts were annotated with gene descriptions or gene ontology terms by sequence similarity analyses against several public databases (Uniprot, NR and Nt at NCBI, and KEGG). Furthermore, we identified key enzyme genes involved in biosynthesis of lignin and phenylethanoid glycosides (PhGs) which are known to be the primary active ingredients. Four phenylalanine ammonia-lyase (PAL) genes, the first key enzyme in lignin and PhG biosynthesis, were identified based on sequences comparison and phylogenetic analysis. Two biosynthesis pathways of PhGs were also proposed for the first time. CONCLUSIONS: In all, we completed a global analysis of the C. deserticola fleshy stem transcriptome using RNA-seq technology. A collection of enzyme genes related to biosynthesis of lignin and phenylethanoid glysides were identified from the assembled and annotated transcripts, and the gene family of PAL was also predicted. The sequence data from this study will provide a valuable resource for conducting future phenylethanoid glysides biosynthesis researches and functional genomic studies in this important medicinal plant.

[Ecological risk evaluation of heavy metals of the typical dredged mud in Shanghai].

In order to discuss the potential ecological risk of heavy metals of the typical dredged mud in Shanghai, the Hakanson potential ecological risks method was used to analyse and assess the potential ecological risks of heavy metals, including Hg, Cd, Cu, Pb, As,Cr and Zn in dredged mud from the following three areas-the dock apron of Huangpu River, the mouth of the Yangtze River and inland waterways. The results showed that the mean values of ecological risk index (Er(i)) of the seven heavy metals are 20.05, 17.49, 8.82, 5.71, 4.68, 1.74 and 1.13, respectively, all of which belonged to the low ecological risk; Cd (one location in inland waterways) and Hg (three locations in the mouth of the Yangtze River and one location in inland waterways) are the most hazardous elements, with the Er(i) > 40, which belonged to the medium ecological risk or the high ecological risk, and other elements belonged to the low ecological risk. From the results of ecological risk indices(ERI) of the heavy metals in Shanghai dredged mud, the risk of the heavy metals belonged to the low ecological risk. The ERI of inland waterways, the mouth of the Yangtze River and the dock apron of the Huangpu River were 81.4, 57.7 and 52.5, respectively, which all belong to the low ecological risk.