ABSTRACT
The excellent stability of covalent organic frameworks (COFs) and the diversity of metal organic frameworks (MOFs) make MOF/COF hybrid materials promising candidates for chromatographic stationary phases. In this paper, a TpBD/UiO-66-NH2 hybrid material was synthesized through a Schiff-base reaction between TpBD COFs and UiO-66-NH2 MOFs; characterized using Fourier-transform infrared spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy; and bonded to a capillary to prepare a TpBD/UiO-66-NH2-bonded open tubular capillary electrochromatography (OT-CEC) column. Results suggested that the hybrid material had the crystal morphology of a single COF and MOF, a micro-mesoporous structure, and good thermal stability. The inner surface of the OT-CEC column was tightly and uniformly distributed with the stationary phase (â¼1.5 µm). The baseline separation of 13 amino acids and three families (4 acidic antibiotics, 4 preservatives and 6 sulfonamides) of emerging pollutant mixtures was achieved due to the synergistic effect of TpBD and UiO-66-NH2 in the stationary phase. The OT-CEC column showed good reproducibility and stability with relative standard deviations of migration time and resolutions in the range of 1.17-3.93% and 1.79-4.31%, respectively.
ABSTRACT
A novel chiral covalent organic framework (CCOF) was synthesized with an imine covalent organic framework TpBD (synthesized via Schiff-base reaction between phloroglucinol (Tp) and benzidine (BD)) modified using (1S)-(+)-10-camphorsulfonyl chloride as chiral ligand by chemical bonding method for the first time, and was characterized by X-ray diffraction, Fourier-transform infrared spectra, X-ray photoelectron spectroscopy, nitrogen adsorption/desorption, thermogravimetry analysis, and zeta-potential. The results revealed that the CCOF had good crystallinity, high specific surface area and good thermal stability. Then, the CCOF was employed as stationary phase in open-tubular capillary electrochromatography (OT-CEC) column (the CCOF-bonded OT-CEC column) for enantioseparation of 21 single chiral compounds (12 natural amino acids including acidic, neutral and basic, 9 pesticides including herbicides, insecticides and fungicides) and simultaneous enantioseparation of mixture amino acids and pesticides with similar structures or properties. Under the optimized CEC conditions, all the analytes reached the baseline separation with high resolutions of 1.67-25.93 and selectivity factors of 1.06-3.49 in 8 min. Finally, the reproducibility and stability of the CCOF-bonded OT-CEC column were measured. Relative standard deviations (RSDs) of retention time and separation efficiency were 0.58-4.57% and 1.85-4.98%, and not obviously changed after 150 runs. These results demonstrate that COFs-modified OT-CEC explore a promising method to separate chiral compounds.
ABSTRACT
Traditional batch configuration is not sustainable due to catalyst leaching and ineffective recovery. Herein, a novel membrane-based catalyst with oxygen vacancies is developed, which assembled metal-organic-framework cobalt ferrite nanocrystals (MOF-d CoxFe3-xO4) on polyvinylidene fluoride membrane to activate peroxymonosulfate (PMS) for catalytic degradation of emerging pollutants. MOF-d CoxFe3-xO4 are synthesized by one-step pyrolysis using Co/Fe bimetallic organic frameworks (CoxFe3-x bi-MOF) with tunable cobalt content as a template (x/3-x represented the molar ratio of Co and Fe in MOF). Intriguingly, MOF-d Co1.75Fe1.25O4 membrane exhibits excellent PMS activation efficiency as indicated by 95.12% removal of the probe chemical (bisphenol A) at 0.5 mM PMS (â¼100 L m-2 h-1 at the loading of 10 mg), which is significantly higher than the traditional Co1.75Fe1.25O4 suspension system (34.16%). Experimental results show that the membrane has excellent anti-interference ability to anions and dissolved organic matter, and can effectively degrade a variety of emerging pollutants, and its performance is not inhibited by the change of solution pH (3-9) or the long-term (20 h) continuous flow operation. EPR and quenching experiments show that catalytic degradation is the result of the synergistic effect of radicals and non-radicals. The oxygen vacancy-mediated mechanism can explain the formation of active substances, and the formation of 1O2 plays an important role in the degradation of bisphenol A. This study provides a membrane-based strategy for effective and sustainable removal of emerging pollutants.
Subject(s)
Environmental Pollutants , Metal-Organic Frameworks , Catalysis , Metal-Organic Frameworks/chemistry , Oxygen , Peroxides/chemistryABSTRACT
OBJECTIVES: This study aimed to evaluate the diagnostic performance of magnetic resonance perfusion-weighted imaging (PWI) as a noninvasive method to assess post-treatment radiation effect and tumor progression in patients with glioma. METHODS: A systematic literature search was performed in the PubMed, Cochrane Library, and Embase databases up to March 2020. The quality of the included studies was assessed by the quality assessment of diagnostic accuracy studies 2. Data were extracted to calculate sensitivity, specificity, and diagnostic odds ratio (DOR), 95% Confidence interval (CI) and analyze the heterogeneity of the studies (Spearman correlation coefficient, I2 test). We performed meta-regression and subgroup analyses to identify the impact of study heterogeneity. RESULTS: Twenty studies were included, with available data for analysis on 939 patients and 968 lesions. All included studies used dynamic susceptibility contrast (DSC) PWI, four also used dynamic contrast-enhanced PWI, and three also used arterial spin marker imaging PWI. When DSC was considered, the pooled sensitivity and specificity were 0.83 (95% CI, 0.79 to 0.86) and 0.83 (95% CI, 0.78 to 0.87), respectively; pooled DOR, 21.31 (95% CI, 13.07 to 34.73); area under the curve (AUC), 0.887; Q∗, 0.8176. In studies using dynamic contrast-enhanced, the pooled sensitivity and specificity were 0.73 (95% CI, 0.66 to 0.80) and 0.80 (95% CI, 0.69 to 0.88), respectively; pooled DOR, 10.83 (95% CI, 2.01 to 58.43); AUC, 0.9416; Q∗, 0.8795. In studies using arterial spin labeling, the pooled sensitivity and specificity were 0.79 (95% CI, 0.69 to 0.87) and 0.78 (95% CI, 0.67 to 0.87), respectively; pooled DOR, 15.63 (95% CI, 4.61 to 53.02); AUC, 0.8786; Q∗, 0.809. CONCLUSIONS: Perfusion magnetic resonance imaging displays moderate overall accuracy in identifying post-treatment radiation effect and tumor progression in patients with glioma. Based on the current evidence, DSC-PWI is a relatively reliable option for assessing tumor progression after glioma radiotherapy.