Enhanced protonation ability of covalent organic frameworks via N,O-bidentate chelation for photocatalytic H2 evolution.

Inspired by the bidentate coordination chemistry of metal ions, we incorporated hydroxyl (OH) and methoxy (OMe) groups into the skeleton of imine-linked COFs to improve their protonation ability via intramolecular hydrogen bonds (O-H⋯NC). In comparison with the pristine COFs possessing monodentate nitrogen coordination sites, OH and OMe functionalized COFs with (N,O)-bidentate chelating sites exhibited up to 13.8 times faster photocatalytic hydrogen evolution rates (HERs).

Construction of Ultrastable Nonsubstituted Quinoline-Bridged Covalent Organic Frameworks via Rhodium-Catalyzed Dehydrogenative Annulation.

Exploring new routes to lock the dynamic C=N bonds in imine-linked covalent organic frameworks (COFs) is highly desired for enhancing their stability and functionality. Herein, a novel C=N bridge locking strategy via rhodium-catalyzed [4+2] annulation is developed to construct nonsubstituted quinoline-linked COFs (NQ-COFs). The notable feature of this strategy includes high C=N conversion efficiency, oxidant-free, and generality for synthesis of a variety of NQ-COFs with high chemical stability. Particularly, after post-synthetic modification, the crystallinity, topology, and porosity of pristine imine-linked COFs are well retained. When used as photocatalysts, NQ-COFs display better visible light absorption and carriers' separation efficiency due to enhanced in-plane π conjugation ability, as well as more facile generation of superoxide anion radicals than their counterparts, thus leading to efficient synthesis of 2,4,6-tris(aryl)pyridines, benzimidazole, and sulfoxide derivatives.

[Effect of body mass index, waist-to-height ratio and dietary fat on serum leptin level of middle-age adult in Zhejiang Province].

OBJECTIVE: To investigate the association between body mass index(BMI), waist-to-height ratio(WHtR) and dietary fat with serum leptin concentration. METHODS: A three-day 24-h dietary recall method was conducted on 513 participants aged30-65 years who were randomly selected from Zhejiang Province in 2014 to investigate usual fat intake. In addition, parameters including height, weight, waist and serum leptinconcentration of participants were measured and determined by physical examination and laboratory detection. RESULTS: Concentration of serum leptin in women was significantly higher than that in men( P< 0. 001). Both BMI and WHtR were positively correlated with serum leptin level( men: r=0. 488 and 0. 576, women: r =0. 453 and 0. 333, P<0. 0001), but only correlation of WHtR that men(r=0. 354, P<0. 0001) and BMI in women(r=0. 321, P< 0. 0001) remained when BMI and WHtR were controlled respectively. Standardized partial regression coefficient of WHtR(ß =0. 27) was higher than that of BMI(ß=0. 21) in men while in women the coefficient of BMI(ß=0. 26)was higher than that of WHtR(ß = 0. 20). Serum leptin level was negatively correlated with total energy, total fat and MUFA in men(P<0. 05), but the correlation between total energy and leptin was disappeared when WHtR was controlled for. Serum leptin level was positively correlated with the proportion of PUFA from total energy and(PUFA +MUFA) ∶ SFA in women(P<0. 05), while only the correlation between the proportion of PUFA from total energy and leptin remained when BMI was controlled for. CONCLUSION: Obesity degree was gender-specifically positively correlated with serum leptin level, which indicated different obesity indicators should be used for men and women when analyzing serum leptin. Serum leptin was negatively correlated with total fat and MUFA in men, while positively correlated with the proportion of PUFA from total energy in women.