A novel zirconium-based metal-organic framework covalently modified by methyl pyridinium bromide for mild and co-catalyst free conversion of CO2 to cyclic carbonates.

Building metal-organic frameworks (MOFs) covalently modified by onium halides is a promising approach to develop efficient MOF-based heterogeneous catalysts for the cycloaddition of CO2 to epoxides (CCE) into cyclic carbonates. Herein, we report a novel zirconium-based MOF covalently modified by methyl pyridinium bromide, Zr6O4(OH)4(MPTDC)2.2(N-CH3-MPTDC)3.8Br3.8 ((Br-)CH3-Pyridinium-MOF-1), where MPTDC denotes 3-methyl-4-pyridin-4-yl-thieno[2,3-b] thiophene-2,5-dicarboxylate. The structure and composition of this complex were fully characterized with PXRD, NMR, XPS, TEM and so on. CO2 adsorption experiments show that (Br-)CH3-Pyridinium-MOF-1 has a higher affinity for CO2 than its electrically neutral precursor, which should be attributed to the fact that charging frameworks containing pyridinium salt have stronger polarization to CO2. (Br-)CH3-Pyridinium-MOF-1 integrated reactive Lewis acid sites and Br- nucleophilic anions and exhibited efficient catalytic activity for CCE under ambient pressure in the absence of co-catalysts and solvents. Furthermore, (Br-)CH3-Pyridinium-MOF-1 was recycled after five successive cycles without substantial loss in catalytic activity. The corresponding reaction mechanism also was speculated.

A high-resolution summary of Cambrian to Early Triassic marine invertebrate biodiversity.

One great challenge in understanding the history of life is resolving the influence of environmental change on biodiversity. Simulated annealing and genetic algorithms were used to synthesize data from 11,000 marine fossil species, collected from more than 3000 stratigraphic sections, to generate a new Cambrian to Triassic biodiversity curve with an imputed temporal resolution of 26 ± 14.9 thousand years. This increased resolution clarifies the timing of known diversification and extinction events. Comparative analysis suggests that partial pressure of carbon dioxide (Pco2) is the only environmental factor that seems to display a secular pattern similar to that of biodiversity, but this similarity was not confirmed when autocorrelation within that time series was analyzed by detrending. These results demonstrate that fossil data can provide the temporal and taxonomic resolutions necessary to test (paleo)biological hypotheses at a level of detail approaching those of long-term ecological analyses.

[Schistosomiasis monitoring and its cost in population in Danyang City, 2010-2014].

OBJECTIVE: To explore the monitoring method of the infection source of schistosomiasis in the population of the schistosomiasis transmission-interrupted area with Oncomelania hupensis snails. METHODS: The changes of schistosomiasis among the population were investigated by using the active and passive monitoring methods in Danyang City from 2010 to 2014, and the cost-effectiveness of the two monitoring methods was evaluated. RESULTS: Totally 49,277 persons were detected for schistosomiasis by dipstick dye immunoassay (DDIA) from 2010 to 2014 and 608 cases were positive, and the positive rate was 1.23%. There were no positive persons by etiology detections. The positive rates of active and passive monitoring methods were 1.61% and 1.13%, respectively and there was a significant difference between them (χ² = 15.982, P < 0.05). The average cost per positive case of the active monitoring was higher than that of the passive monitoring without considering the costs of the mobilization and labor. CONCLUSION: In the schistosomiasis transmission-interrupted area with snails, the active and passive monitoring methods need to be combined in the future.