Despite numerous inherent merits of metal–organic frameworks (MOFs), structural fragility has imposed great restrictions on their wider involvement in many applications, such as in catalysis. Herein, ...a strategy for enhancing stability and enabling functionality in a labile Zr(IV)‐MOF has been proposed by in situ porphyrin substitution. A size‐ and geometry‐matched robust linear porphyrin ligand 4,4′‐(porphyrin‐5,15‐diyl)dibenzolate (DCPP2−) is selected to replace the 4,4′‐(1,3,6,8‐tetraoxobenzolmn3,8phenanthroline‐2,7(1H,3H,6H,8H)‐diyl)dibenzoate (NDIDB2−) ligand in the synthesis of BUT‐109(Zr), affording BUT‐110 with varied porphyrin contents. Compared to BUT‐109(Zr), the chemical stability of BUT‐110 series is greatly improved. Metalloporphyrin incorporation endows BUT‐110 MOFs with high catalytic activity in the photoreduction of CO2, in the absence of photosensitizers. By tuning the metal species and porphyrin contents in BUT‐110, the resulting BUT‐110‐50%‐Co is demonstrated to be a good photocatalyst for selective CO2‐to‐CO reduction, via balancing the chemical stability, photocatalytic efficiency, and synthetic cost. This work highlights the advantages of in situ ligand substitution for MOF modification, by which uniform distribution and high content of the incoming ligand are accessible in the resulting MOFs. More importantly, it provides a promising approach to convert unstable MOFs, which mainly constitute the vast MOF database but have always been neglected, into robust functional materials.
The in situ porphyrin substitution strategy is developed for modifying labile interpenetrated BUT‐109(Zr), affording BUT‐110 with enhanced chemical stability and photocatalytic activity. By tuning the species and contents of metalloporphyrin in BUT‐110, some of the BUT‐110 MOFs may serve as potential photocatalysts for selective CO2‐to‐CO reduction, in the absence of photosensitizer.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
We design and synthesize two stable Zr(
iv
)-based metal-organic frameworks with high proton conductivity, namely
BUT-76
and
BUT-77
, which are constructed with the same sulfonic acid containing ...ligand and 8/12 connected Zr
6
clusters. The proton conductivity of these two materials at 80 °C and 100% relative humidity (RH) can reach 8.55 × 10
−3
and 3.08 × 10
−2
S cm
−1
correspondingly. Moreover, both
BUT-76
and
BUT-77
can maintain their high conductivity and framework integrity for at least 120 hours under the test conditions. XRD diffraction measurements and comprehensive molecular simulations are conducted to explore how the increased connectivity of Zr
6
clusters can significantly enhance the proton conductivity of the materials by changing the proton carrier concentration and hydrogen-bonding network. Furthermore, the
BUT-77
mixed-matrix membrane shows a proton conductivity value of 1.25 × 10
−3
S cm
−1
(80 °C, 100% RH). This work not only presents promising candidate materials for proton exchange membranes, but also demonstrates an example to use MOF as a platform to reveal the relationship between structural features and proton conductivity.
Improving proton conductivity in Zr-MOFs through enhancing metal cluster connectivity.
Fires lead to dramatic shifts in ecosystems and have a large impact on the biota. Soil organisms, especially soil fauna, are often used as indicators of environmental change. At present, minimal ...attention has been paid to using soil fauna as an indicator of environmental change after a fire. Here, a field survey of burnt herbaceous vegetation in semi-arid areas was conducted to determine the response of soil arthropods to fire and their short–term recovery after fire. Overall, the abundance and biomass of soil arthropods was more sensitive to fire than the number of groups. The number of soil arthropod groups, especially the dominant groups (mites and springtails), was not significantly affected by wildfires. At the unburned site, soil arthropod abundance showed significant seasonal shifts that may be related to the vegetation properties, temperature, and precipitation caused by seasonal changes. In contrast, soil arthropods at the burnt sites showed a delayed recovery and had only reached 56%–82%, 17%–54%, and 91%–190% of the biomass in the unburnt forest at the 3, 6, and 9 months after the burning event. Our findings of soil arthropod abundance changes in the present study suggest that fire-induced changes in soil and vegetation properties (e.g., AN, LT, and VC) were crucial factors for the changes in soil arthropod abundance in this semi-arid grassland. We conclude that fire disturbance reduces the seasonal sensitivity of soil arthropods by altering their habitat. This study furthers our understanding of wildfire impact recovery by documenting the short-term temporal dynamics of soil arthropods.
•Soil moisture has a bilateral asymmetry pattern across the permanent gully.•The effect of distance to the gully was stronger than that of soil depth.•Gully edge effect is proposed for the fragmented ...landscape.•Gully edge effect is adverse for soil water conservation.
Describing and mapping soil water content (SWC) distribution are required to understand and explain the hydrological phenomena at various spatial scales. Soil drought in the hilly and gully regions of Loess Plateau reduces agricultural production and plants biomass, which has attracted great attention but few studies associated it with the gullied terrain. To understand the SWC distribution pattern in the slope–gully system, we established a cross-section transect for SWC observation across a permanent gully and acquired 23 occasions of SWC data in the periods from October 2014 to September 2018. The standardized beta coefficient in stepwise multiple linear regression was employed to determine the strength of the effect of the selected variables (soil textural separates, soil depth, relative height, distance to the gully and saturated hydraulic conductivity) on SWS distribution. Spectral and cross-spectral analysis were performed on the time series of SWC to evaluate the cyclical behavior and the similarity for adjacent sites, respectively. The following results were obtained: First, the SWC distribution had a bilateral asymmetrical pattern across the gully, which constituted a specific and detailed content of spatial variability of SWC. Second, soil water storage in the slope–gully system was primarily affected by soil texture, meanwhile, the effect of distance to the gully was stronger than that of soil depth. Third, the SWC of the adjacent pair sites presented consistent periodic behavior. The cross-spectral analysis indicated a dissimilar pattern for soil layer of 0–60 cm and deep synchrony for the other depth layers. In conclusion, the gully edge effect aggravated the SWC status in the south bank and caused a bilateral asymmetrical pattern in the slope–gully system. These results improved our knowledge on the complicated distribution of SWC in the gullied region. Moreover, the results indicate that ignoring the nearby areas of a permanent gully in a catchment is inappropriate when investigating soil water resources.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•A facile mixed-ligand approach is adopted to functionalize IRMOF-74-IV with metalloporphyrin for multivariate mesoporous analogs.•Compared with IRMOF-74-IV, the functionalized ...analogs show improved stability and performance in photocatalytic CO2 reduction.•The photocatalytic performance of IRMOF-74-IV analogs could be optimized by tuning the contents and species of metalloporphyrin.
Metal-organic frameworks (MOFs) are widely employed as functional materials in various fields, while intriguing properties for specific applications have been pursued all along with their development. Herein, we adopt a ligand substitution strategy to functionalize the mesoporous IRMOF-74-IV for multivariate MOF catalysts. With similar size and geometry, the porphyrin ligand 4,4′-(porphyrin-5,15-diyl)bis(2-hydroxybenzolate) (PBHB2–) was mixed with the 3,3′″-dihydroxy-2′,2″,5′,5″-tetramethyl-1,1′:4′,1″:4″,1″′-quaterphenyl-4,4″′-dicarboxylate (L-IV2–) ligand in synthesis, giving porphyrin functionalized IRMOF-74-IV analogs. Compared with IRMOF-74-IV, the IRMOF-74-IV-PBHBX-M series show improved stability and performance in photocatalytic CO2 reduction. After tuning the contents of porphyrin ligand and the species of metal ion, IRMOF-74-IV-PBHB45%-Cu demonstrates to be the best as an efficient photocatalyst for the CO2-to-CO conversion. This work has achieved to tailor extant MOFs through a mixed-ligand approach, which would contribute to more multivariate materials and unlock new opportunities for their applications.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Despite numerous inherent merits of metal-organic frameworks (MOFs), structural fragility has imposed great restrictions on their wider involvement in many applications, such as in catalysis. Herein, ...a strategy for enhancing stability and enabling functionality in a labile Zr(IV)-MOF has been proposed by in situ porphyrin substitution. A size- and geometry-matched robust linear porphyrin ligand 4,4'-(porphyrin-5,15-diyl)dibenzolate (DCPP
) is selected to replace the 4,4'-(1,3,6,8-tetraoxobenzolmn3,8phenanthroline-2,7(1H,3H,6H,8H)-diyl)dibenzoate (NDIDB
) ligand in the synthesis of BUT-109(Zr), affording BUT-110 with varied porphyrin contents. Compared to BUT-109(Zr), the chemical stability of BUT-110 series is greatly improved. Metalloporphyrin incorporation endows BUT-110 MOFs with high catalytic activity in the photoreduction of CO
, in the absence of photosensitizers. By tuning the metal species and porphyrin contents in BUT-110, the resulting BUT-110-50%-Co is demonstrated to be a good photocatalyst for selective CO
-to-CO reduction, via balancing the chemical stability, photocatalytic efficiency, and synthetic cost. This work highlights the advantages of in situ ligand substitution for MOF modification, by which uniform distribution and high content of the incoming ligand are accessible in the resulting MOFs. More importantly, it provides a promising approach to convert unstable MOFs, which mainly constitute the vast MOF database but have always been neglected, into robust functional materials.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
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The emergence and spread of multidrug-resistant (MDR) Gram negative bacteria presents a serious threat for public health. Novel antimicrobials that could overcome the resistance ...problems are urgently needed. UDP-3-O-(R-3-hydroxymyristol)-N-acetylglucosamine deacetylase (LpxC) is a cytosolic zinc-based deacetylase that catalyzes the first committed step in the biosynthesis of lipid A, which is essential for the survival of Gram-negative bacteria. Our efforts toward the discovery of novel LpxC inhibitors are presented herein.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Coal is the primary energy resource in China, with the raw coal production reaching 2.8 billion tons in 2008. However, great amount of coalmine methane is released during coal exploitation, which ...runs up to over 3.5 billion cubic meters. To minimize environmental pollution caused by coalmine methane and to promote resource utilization, various systems for utilizing coalmine methane energy are developed in China. Common types of such systems include power generation system utilizing coalmine methane, combined-heat-and-power system of coalmine methane, thermal energy provision system of coalmine methane, and fuel-gas provision system, etc. This paper describes elements, characteristics, and applicability of these systems and presents thermal economy analysis to specific system. Thermal economic indexes, such as exergic efficiency and exergic losses of specific coalmine methane energy utilization system are obtained. These data are very useful in finding the way to make further progress in improving thermal economy of coalmine methane energy utilization systems as well as providing technical support to make tradeoffs among those systems. In addition, the possibility of serving coalmine methane energy utilization systems as distributed energy resource is discussed and potential problems summarized. Generally speaking, these efforts are practical to promote coalmine methane energy utilization in China.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Although estuarine tidal marshes are important contributors to the emission of greenhouse gases into the atmosphere, the relationship between carbon dioxide（CO2）, methane（CH4）emission, and ...environmental factors, with respect to estuarine marshes, has not been clarified thoroughly. This study investigated the crucial factors controlling the emission of CO2 and CH4from a freshwater marsh and a brackish marsh located in a subtropical estuary in southeastern China, as well as their magnitude. The duration of the study period was November 2013 to October 2014. Relevant to both the field and incubation experiments, the CO2 and CH4emissions from the two marshes showed pronounced seasonal variations. The CO2 and CH4emissions from both marshes demonstrated significant positive correlations with the air/soil temperature（p 〈 0.01）, but negative correlations with the soil electrical conductivity and the pore water/tide water Cl-and SO42- （p 〈 0.01）. The results indicate no significant difference in the CO2 emissions between the freshwater and brackish marshes in the subtropical estuary, whereas there was a difference in the CH4 emissions between the two sites（p 〈 0.01）. Although future sea-level rise and saltwater intrusion could reduce the CH4 emissions from the estuarine freshwater marshes, these factors had little effect on the CO2 emissions with respect to an increase in salinity of less than 5‰. The findings of this study could have important implications for estimating the global warming contributions of estuarine marshes along differing salinity gradients.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
BACKGROUND: V entricular arrhythmia(VA) is one of the most common complications of myocardial infarction(MI), and ventricular tachycardia and fi brillation are the main causes for sudden cardiac ...death. This study aimed to explore the effect of ramipril on the occurrence of VA and its mechanism after MI in rabbits.METHODS: Twenty-four New Zealand rabbits purchased from the Wuhan Laboratory Animal Research Center were divided into three groups: sham-operated(SHAM) group(n=8), MI group(n=8) and MI with ramipril(RAM) group(n=8). Rabbits in the SHAM group received a median sternotomy without ligation of the left ventricular coronary artery. Rabbits in the MI and RAM groups received a median sternotomy followed by ligation of the left coronary artery. The successful anterior MI was confi rmed by elevation of the ST segment with more than 0.2 mV in lead II and III. After MI, rabbits in the RAM group were fed with intragastric ramipril(1 mg/kg per day) for 12 weeks. Before and 12 weeks after MI in the three groups, ventricular tachycardia or fi brillation(VT/VF) episodes and MAP in cadiocytes of the epicardium, mid-myocardium and endocardium were recorded by a multichannel physiograph. Student’s t test and ANOVA were used for statistical analysis.RESULTS: VT/VF episodes were decreased more markedly in the RAM group than in the MI group after 12 weeks(2.6±0.8 vs. 12.4±2.9, P<0.05). Twelve weeks after MI, the duration of repolarization for 90%(APD90) of three-tier ventricular myocytes in the MI group was longer than that before MI(258.2±21.1 vs. 230.1±23.2, 278.0±23.8 vs. 245.8±25.4, 242.6±22.7 vs. 227.0±21.7, P<0.05). However, the APD90 was not signif icantly different at 12 weeks before and after MI in the RAM group(P>0.05). Moreover, the transmural dispersion of repolarization(TDR) was increased more markedly 12 weeks after MI in the MI group than in the SHAM and RAM groups(36.2±10.2 vs. 18.7±6.2, 24.9±8.7, P<0.05). But the TDR was not signifi cantly different between the RAM and SHAM groups(18.7±6.2 vs. 24.9±8.7, P>0.05).CONCLUSION: Ramipril may reduce the incidence of malignant ventricular arrhythmia via improvement of transmembrance repolarization heterogeneity after MI.
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FFLJ, NUK, ODKLJ, UL, UM, UPUK
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