There have been extensive efforts to synthesize crystalline covalent triazine‐based frameworks (CTFs) for practical applications and to realize their potential. The phosphorus pentoxide ...(P2O5)‐catalyzed direct condensation of aromatic amide instead of aromatic nitrile to form triazine rings. P2O5‐catalyzed condensation was applied on terephthalamide to construct a covalent triazine‐based framework (pCTF‐1). This approach yielded highly crystalline pCTF‐1 with high specific surface area (2034.1 m2 g−1). At low pressure, the pCTF‐1 showed high CO2 (21.9 wt % at 273 K) and H2 (1.75 wt % at 77 K) uptake capacities. The direct formation of a triazine‐based COF was also confirmed by model reactions, with the P2O5‐catalyzed condensation reaction of both benzamide and benzonitrile to form 1,3,5‐triphenyl‐2,4,6‐triazine in high yield.
A covalent triazine‐based framework was synthesized by phosphorus pentoxide (P2O5)‐catalyzed direct condensation of aromatic amides to form a triazine ring. Highly crystalline covalent triazine frameworks (pCTF‐1) were produced with high specific surface area (2034.1 m2 g−1). At low pressure, pCTF‐1 shows a high carbon dioxide (CO2) uptake capacity of 21.9 wt % at 273 K and a hydrogen (H2) uptake capacity of 1.75 wt % at 77 K.
Developing efficient and durable electrocatalysts is key to optimizing the electrocatalytic hydrogen evolution reaction (HER), currently one of the cleanest and most sustainable routes for producing ...hydrogen. Here, a unique and efficient approach to fabricate and embed uniformly dispersed Ir nanoparticles in a 3D cage‐like organic network (CON) structure is reported. These uniformly trapped Ir nanoparticles within the 3D CON (Ir@CON) effectively catalyze the HER process. The Ir@CON electrocatalyst exhibits high turnover frequencies of 0.66 and 0.20 H2 s−1 at 25 mV and small overpotentials of 13.6 and 13.5 mV while generating a current density of 10 mA cm−2 in 0.5 m H2SO4 and 1.0 m KOH aqueous solutions, respectively, as compared to commercial Pt/C (18 and 23 mV) and Ir/C (20.7 and 28.3 mV). More importantly, the catalyst shows superior stability in both acidic and alkaline media. These results highlight a potentially powerful approach for the design and synthesis of efficient and durable electrocatalysts for HER.
Encapsulating iridium nanoparticles inside a 3D cage‐like organic network, the prepared catalyst (Ir@CON) is evaluated as an efficient and durable electrocatalyst for the hydrogen evolution reaction. This new study should provide insights to guide the design and development of materials for future organic and hybrid materials for electrocatalysis.
Solid-state reaction of organic molecules holds a considerable advantage over liquid-phase processes in the manufacturing industry. However, the research progress in exploring this benefit is largely ...staggering, which leaves few liquid-phase systems to work with. Here, we show a synthetic protocol for the formation of a three-dimensional porous organic network via solid-state explosion of organic single crystals. The explosive reaction is realized by the Bergman reaction (cycloaromatization) of three enediyne groups on 2,3,6,7,14,15-hexaethynyl-9,10-dihydro-9,10-1,2benzenoanthracene. The origin of the explosion is systematically studied using single-crystal X-ray diffraction and differential scanning calorimetry, along with high-speed camera and density functional theory calculations. The results suggest that the solid-state explosion is triggered by an abrupt change in lattice energy induced by release of primer molecules in the 2,3,6,7,14,15-hexaethynyl-9,10-dihydro-9,10-1,2benzenoanthracene crystal lattice.
Boron (B)-nitrogen (N)-phosphorus (P) doped GnPs (BNP-GnPs) were synthesized by Poly(anilineboronic acid, PABA), which is one of the conducting polymers and acts as a feedstock for BNP doping, was ...in-situ grafted to edge-amine functionalized GnPs (A-GnPs). After heat-treatment, the resultant BNP-GnPs demonstrated significantly improved electrocatalytic activity towards the oxygen reduction reaction, suggesting that the BNP-GnPs can be one of the best alternatives to precious Pt-based electrocatalysts.
Display omitted
•Boron (B)-nitrogen (N)-phosphorus (P) doped graphene nanoplatelets (GnPs) were prepared.•BNP-GnPs were realized by edge-grafting of poly(anilineboronic acid, PABA) and subsequent annealing.•The structure of BNP-GnPs was confirmed by spectroscopic and microscopic analyses.•The BNP-GnPs demonstrated significantly improved electrocatalytic activity towards the oxygen reduction reaction.•BNP-GnPs can be one of the best alternatives to precious Pt-based electrocatalysts.
Doping with foreign atoms is a powerful technique for modifying the inherent properties of a host materials. In this work, we report a strategy for preparing multiple heteroatom-doped graphene nanoplatelets (GnPs). Poly(anilineboronic acid, PABA), which is one of the conducting polymers, was in-situ grafted to edge-amine functionalized GnPs (A-GnPs) in phosphoric acid. The isolated PABA grafted A-GnPs phosphoric acid salts (PA-GnP salts) were heat-treated at 900 °C under argon atmosphere to yield boron (B)-nitrogen (N)-phosphorus (P) doped GnPs (BNP-GnPs). The structure of the BNP-GnPs was confirmed by various techniques, including transmission electron microscopy, scanning electronic microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy and thermogravimetric analysis. The BNP-GnPs demonstrated significantly improved electrocatalytic activity towards the oxygen reduction reaction, suggesting that BNP-GnPs can be one of the best alternatives to precious Pt-based electrocatalysts.
The prediction skill for the East Asian winter monsoon (EAWM) has been analyzed, using the observations and different climate models that participate in the APEC Climate Center (APCC) multi-model ...ensemble (MME) seasonal forecast. The authors first examined the characteristics of the existing EAWM indices to find a suitable index for the APCC seasonal forecast system. This examination revealed that the selected index shows reasonable prediction skill of EAWM intensity and well-represents the characteristics of wintertime temperature anomalies associated with the EAWM, especially for the extreme cold winters. Although most models capture the main characteristics of the seasonal mean circulation over East Asia reasonably well, they still suffer from difficulty in predicting the interannual variability (IAV) of the EAWM. Fortunately, the POAMA has reasonable skill in capturing the timing and strength of the EAWM IAV and reproduces the EAWM-related circulation anomalies well. The better performance of the POAMA may be attributed to the better skill in simulating the high-latitude forcing including the Siberian High (SH) and Artic Oscillation (AO) and the strong links of the ENSO to the EAWM, compared to other models.
Recently, various studies have been conducted on hydrogen energy as a means of replacing conventional fuels. Polymer electrolyte membrane water electrolyzers (PEMWEs) are being studied as a means of ...producing hydrogen for renewable energy. The PEMWE can be operated over a wider range than other types of water electrolyzers and can be connected to a renewable energy source, such as solar or wind. However, further studies are required because the water accompanying the hydrogen in the cathode presents a problem regarding hydrogen purity and storage. The phenomenon of water transport which is occurred on the PEMWE is analyzed by electro-osmotic drag and diffusion in the membrane. Electro-osmotic drag coefficients which are calculated by mass flow rate of discharged water with hydrogen are compared to the results of previous studies. The results of Electro-osmotic drag coefficient are different from previous studies at each operating condition. This difference is considered to be caused by the capacity of PEMWE such as active area and the number of cell.
•Water is discharged from the cathode when hydrogen production using PEMWE.•The Phenomenon of water transport is caused by water permeation and electro-osmosis.•The discharged water with hydrogen is proportional to the current density.•The Temperature impacts on ratio of water permeation to discharged water.•The Electro-osmotic drag coefficient is calculated according to operating conditions.
Laser-assisted thinning (LAT) and laser-assisted opening (LAO) are performed as part of human in vitro fertilization (IVF) to increase the implantation rate in patients with a poor prognosis and in ...cases of repeated implantation failure. However, an insufficient number of studies have directly compared LAT and LAO using the same methods. Therefore, we compared the effects of LAT and LAO on clinical outcomes according to maternal age in patients with repeated implantation failure. This retrospective study was performed in 509 IVF cycles (458 patients). The cycles were divided based on maternal age and the method used (< 38 years LAT,
n
= 119 vs. LAO,
n
= 179 and ≥ 38 years LAT,
n
= 72 vs. LAO,
n
= 139). Cleavage-stage embryos before transfer were either thinned or opened using a 1.46-μm noncontact diode laser. We compared the implantation rates and pregnancy outcomes of cycles between LAT and LAO according to maternal age. The characteristics of patients did not differ significantly among the groups (
p
> 0.05), with the exception of mixed factor infertility, which was more common in the LAT group than in the LAO group among patients < 38 years of age (10.1% vs. 2.8%,
p
= 0.008). The LAT and LAO groups showed similar rates of biochemical pregnancy, clinical pregnancy, ongoing pregnancy, abortion, implantation, singleton pregnancy, and twin pregnancy (
p
> 0.05). In conclusion, LAT and LAO had similar clinical outcomes. Therefore, we did not find any evidence that LAT is superior to LAO. In fact, the patients ≥ 38 years of age who underwent LAO tended to have a lower abortion rate. Further study is necessary to confirm these results in a larger population.
Using 32 CMIP5（Coupled Model Intercomparison Project Phase 5） models, this study examines the veracity in the simulation of cloud amount and their radiative effects（CREs） in the historical run driven ...by observed external radiative forcing for 1850-2005, and their future changes in the RCP（Representative Concentration Pathway） 4.5 scenario runs for2006-2100. Validation metrics for the historical run are designed to examine the accuracy in the representation of spatial patterns for climatological mean, and annual and interannual variations of clouds and CREs. The models show large spread in the simulation of cloud amounts, specifically in the low cloud amount. The observed relationship between cloud amount and the controlling large-scale environment are also reproduced diversely by various models. Based on the validation metrics,four models-ACCESS1.0, ACCESS1.3, Had GEM2-CC, and Had GEM2-ES-are selected as best models, and the average of the four models performs more skillfully than the multimodel ensemble average.All models project global-mean SST warming at the increase of the greenhouse gases, but the magnitude varies across the simulations between 1 and 2 K, which is largely attributable to the difference in the change of cloud amount and distribution. The models that simulate more SST warming show a greater increase in the net CRE due to reduced low cloud and increased incoming shortwave radiation, particularly over the regions of marine boundary layer in the subtropics. Selected best-performing models project a significant reduction in global-mean cloud amount of about-0.99% K^-1and net radiative warming of 0.46 W m^-2K^-1, suggesting a role of positive feedback to global warming.
Kish graphite, a waste (called dust) from a steelmaking process, can be simultaneously purified and functionalized by mechanochemical ball‐milling in the presence of iodine. The resultant iodinated ...Kish graphite (I‐Kish‐G) contains low content of impurities and high iodine content (1.83 at%, 16.17 wt%, energy dispersive X‐ray spectroscopy) with high crystallinity. It has high specific surface area (924.3 m2 g−1), indicating that I‐Kish‐G is significantly purified, functionalized, and exfoliated into a few graphitic layers. More importantly, I‐Kish‐G displays outstanding electrocatalytic activity for oxygen reduction reaction with long‐term durability and robustness against methanol crossover and CO poisoning effects in alkaline media.
Using mechanochemical ball‐milling, waste Kish graphite (Kish‐G) is simply converted into high‐quality electrocatalyst for oxygen reduction reaction in alkaline media. Ball‐milling Kish‐G in the presence of iodine simultaneously purifies and functionalizes Kish‐G into iodinated Kish‐G (I‐Kish‐G) with low content of impurities, high iodine content, high degree of crystallinity, and high specific surface area.
Substantial amounts of aluminum (Al), which is one of the most abundant elements and period III post-transition metals, can be incorporated into graphene nanoplatelets (GnPs) by ball-milling graphite ...in the presence of solid Al beads. After thoroughly etching away any unreacted Al residues, the structure and properties of the resultant aluminated GnPs (AlGnPs) were characterized using various analytical techniques including transmission electron microscopy (TEM) and time-of-flight secondary ion mass spectroscopy (TOF-SIMS). The results indicate that AlGnPs contain a considerable amount of Al (30.9 wt%, by TEM energy dispersive X-ray spectrum) and display good dispersibility in various solvents, including water. Next, composite films from aqueous AlGnP/poly(vinyl alcohol) (1/4, wt/wt) solutions were cast and tested for flame retardation. The results indicate that AlGnPs could serve as an outstanding flame retardant that operates by both chemical (condensation) and physical (cooling and blocking) mechanisms. This suggests that AlGnPs may provide a promising option for a new, cost-effective, eco-friendly, yet efficient flame retardant.
Heavily aluminated graphene nanoplatelets (AlGnPs) are produced by mechanochemical ball-milling of graphite with solid aluminum beads. AlGnPs show outstanding flame retardancy via chemical and physical flame retardation mechanisms. Hence, AlGnPs provide a very promising option for cost-effective, eco-friendly, efficient flame retardants. Display omitted
PDF
