Sulfhydryl-Directed Iridium-Catalyzed C–H/Diazo Coupling and Tandem Annulation of Naphthalene-1-thiols

The first sulfhydryl-directed iridium-catalyzed C–H/diazo coupling and tandem annulation of naphthalene-1-thiols has been developed. The framework of naphtho­[1,8-bc]­thiopyrans was constructed in a one-step reaction with good yields. This transformation provides a practical synthetic route for the widely used naphtho­[1,8-bc]­thiopyran derivatives

Use of Ball Drop Casting and Surface Modification for the Development of Amine-Functionalized Silica Aerogel Globules for Dynamic and Efficient Direct Air Capture

Amine-functionalized silica aerogel globules (AFSAGs) were first synthesized via a simple ball drop casting method followed by amine grafting. The effect of grafting time on the structure and CO2 adsorption performance of the AFSAGs was investigated. The CO2 adsorption performance was comprehensively studied by breakthrough curves, adsorption capacity and rates, surface amine loading and density, amine efficiency, adsorption halftime, and cyclic stability. The results demonstrate that prolonging the grafting time does not lead to a significant increase in surface amine content owing to pore space blockage by superabundant amine groups. The CO2 adsorption performance shows obvious dependence on surface amine density, determined by both the surface amine content and specific surface area, and working temperature. AFSAGs with a grafting time of 24 h (AFSAG24) with a moderate surface amine density have optimal CO2 adsorption capacities, which are 1.78 and 2.14 mmol/g at 25 °C with dry and humid 400 ppm CO2, respectively. The amine efficiency of AFSAG24 with low CO2 concentrations, 0.38–0.63 with dry 400 ppm−1% CO2, is the highest among the reported amine-functionalized adsorbents. After estimation with different diffusion models, the CO2 adsorption process of AFSAG24 is governed by film diffusion and intraparticle diffusion. In the range of 1–4 mm, the ball size does not affect the CO2 adsorption capacity of AFSAG24 obviously. AFSAG24 offers significant advantages for practical direct air capture compared with its state-of-the-art counterparts, such as high dynamic adsorption capacity and amine efficiency, excellent stability, and outstanding adaptation to the environment

Synthesis, Structures, and Norbornene ROMP Behavior of <i>o</i>-Aryloxide-N-Heterocyclic Carbene <i>p</i>-Cymene Ruthenium Complexes

Treatment of the <i>o</i>-hydroxyaryl imidazolium proligands (2-OH-3,5-^<i>t</i>Bu₂C₆H₂)­(R)­(C₃H₃N₂)⁺Br^– (R = ^<i>i</i>Pr (<b>1a</b>), ^<i>t</i>Bu (<b>1b</b>), Ph (<b>1c</b>), Mes (<b>1d</b>)) with 3 equiv of Ag₂O afforded the corresponding silver complexes <b>2a</b>–<b>d</b>. The subsequent metal-exchange reactions with [(<i>p</i>-cymene)­RuCl₂]₂ at room temperature yielded the desired <i>o</i>-aryloxide-N-heterocyclic carbene <i>p</i>-cymene ruthenium complexes <b>3a</b>–<b>d</b> in nearly quantitative yields. All the complexes were characterized by ¹H and ¹³C NMR, high-resolution mass spectrometry (HRMS), and elemental analysis. The molecular structure of complex <b>3b</b> was determined by single-crystal X-ray diffraction analysis. The ring-opening metathesis polymerization (ROMP) of norbornene (NBE) with <b>3a</b>–<b>d</b> was studied. Among them, complex <b>3d</b> showed high activity and efficiency toward ROMP of NBE at 85 °C without the need for any cocatalyst, and polymers with very high molecular weight (>10⁶) and narrow molecular weight distributions were obtained. This complex can also catalyze the alternating copolymerization of NBE and cyclooctene (COE)

Flexible Silica Aerogel Composites for Thermal Insulation under High-Temperature and Thermal–Force Coupling Conditions

The objective of this research was to develop a high-performance flexible silica aerogel composite for thermal insulation under high-temperature and thermal–force coupling conditions. Based on synthesis of flexible silica aerogels with methyltrimethoxysilane as the precursor, flexible silica aerogel composites were developed by wet-impregnating ceramic fiber felt. Morphology, microstructure, chemical structure, hydrophobicity, and compression performance evolutions of the flexible silica aerogels and their composite counterparts with temperature revealed that the resulting flexible silica aerogel samples have excellent stability at 900 °C. Flexible silica aerogel composites show 100 and 70% recovery with 50% strain after treatment at 500 and 900 °C, respectively. Thermal insulation performance of the flexible silica aerogel composites was comprehensively studied from different aspects, including thermal conductivity, thermal shield behavior under high-temperature and thermal–force coupling conditions, and thermal shock resistance. Thermal conductivities of the flexible silica aerogel composite at 25–1100 °C are lower than those of most reported aerogel composites. Coupling of force under high temperature leads to degradation of thermal insulation performance, owing to deformation with compression. The synthesis method of the flexible silica aerogel is facile and inspiring, and the flexible silica aerogel composites have promising prospects in thermal insulation under high-temperature and thermal-stress coupling conditions, such as suppressing thermal runaway propagation of lithium-ion batteries

Flexible Silica Aerogel Composites for Thermal Insulation under High-Temperature and Thermal–Force Coupling Conditions

The objective of this research was to develop a high-performance flexible silica aerogel composite for thermal insulation under high-temperature and thermal–force coupling conditions. Based on synthesis of flexible silica aerogels with methyltrimethoxysilane as the precursor, flexible silica aerogel composites were developed by wet-impregnating ceramic fiber felt. Morphology, microstructure, chemical structure, hydrophobicity, and compression performance evolutions of the flexible silica aerogels and their composite counterparts with temperature revealed that the resulting flexible silica aerogel samples have excellent stability at 900 °C. Flexible silica aerogel composites show 100 and 70% recovery with 50% strain after treatment at 500 and 900 °C, respectively. Thermal insulation performance of the flexible silica aerogel composites was comprehensively studied from different aspects, including thermal conductivity, thermal shield behavior under high-temperature and thermal–force coupling conditions, and thermal shock resistance. Thermal conductivities of the flexible silica aerogel composite at 25–1100 °C are lower than those of most reported aerogel composites. Coupling of force under high temperature leads to degradation of thermal insulation performance, owing to deformation with compression. The synthesis method of the flexible silica aerogel is facile and inspiring, and the flexible silica aerogel composites have promising prospects in thermal insulation under high-temperature and thermal-stress coupling conditions, such as suppressing thermal runaway propagation of lithium-ion batteries

Synthesis, Structures, and Norbornene ROMP Behavior of <i>o</i>-Aryloxide-N-Heterocyclic Carbene <i>p</i>-Cymene Ruthenium Complexes

Treatment of the <i>o</i>-hydroxyaryl imidazolium proligands (2-OH-3,5-^<i>t</i>Bu₂C₆H₂)­(R)­(C₃H₃N₂)⁺Br^– (R = ^<i>i</i>Pr (<b>1a</b>), ^<i>t</i>Bu (<b>1b</b>), Ph (<b>1c</b>), Mes (<b>1d</b>)) with 3 equiv of Ag₂O afforded the corresponding silver complexes <b>2a</b>–<b>d</b>. The subsequent metal-exchange reactions with [(<i>p</i>-cymene)­RuCl₂]₂ at room temperature yielded the desired <i>o</i>-aryloxide-N-heterocyclic carbene <i>p</i>-cymene ruthenium complexes <b>3a</b>–<b>d</b> in nearly quantitative yields. All the complexes were characterized by ¹H and ¹³C NMR, high-resolution mass spectrometry (HRMS), and elemental analysis. The molecular structure of complex <b>3b</b> was determined by single-crystal X-ray diffraction analysis. The ring-opening metathesis polymerization (ROMP) of norbornene (NBE) with <b>3a</b>–<b>d</b> was studied. Among them, complex <b>3d</b> showed high activity and efficiency toward ROMP of NBE at 85 °C without the need for any cocatalyst, and polymers with very high molecular weight (>10⁶) and narrow molecular weight distributions were obtained. This complex can also catalyze the alternating copolymerization of NBE and cyclooctene (COE)

Development of Regular Hydrophobic Silica Aerogel Microspheres for Efficient Oil Adsorption

The objective of this research was to develop new hydrophobic silica aerogel microspheres (HSAMs) with water glass and hexmethyldisilazane for oil adsorption. The effects of the hexmethyldisilazane concentration and drying method on the structure and organic liquid adsorption capacity were investigated. The hexmethyldisilazane concentration of the modification solution did not influence the microstructure and pore structure in a noteworthy manner, which depended more on the drying method. Vacuum drying led to more volume shrinkage of the silica gel microsphere (SGM) than supercritical CO2 drying, thus resulting in a larger apparent density, lower pore volume, narrower pore size distribution, and more compact network. Owing to the large pore volume and pore size, the HSAMs synthesized via supercritical CO2 drying had a larger organic liquid adsorption capacity. The adsorption capacities of the HSAMs with pore volumes of 4.04–6.44 cm3/g for colza oil, vacuum pump oil, and hexane are up to 18.3, 18.9, and 11.8 g/g, respectively, higher than for their state-of-the-art counterparts. The new sorbent preparation method is facile, cost-effective, safe, and ecofriendly, and the resulting HSAMs are exceptional in capacity, stability, and regenerability

The Impact of Clickers Instruction on Cognitive Loads and Listening and Speaking Skills in College English Class

<div><p>Clickers might own a bright future in China if properly introduced although they have not been widely acknowledged as an effective tool to facilitate English learning and teaching in Chinese contexts. By randomly selecting participants from undergraduates in a university in China over four academic years, this study aims to identify the impact of clickers on college English listening and speaking skills, and differences in cognitive loads between clickers and traditional multimedia assisted instruction modes. It was concluded that in China's college English class, compared with multimedia assisted instruction, (1) clickers could improve college English listening skills; (2) clickers could improve college English speaking skills; and (3) clickers could reduce undergraduates' cognitive loads in College English Class. Reasons for the results and defects in this study were also explored and discussed, based on learning, teaching and cognitive load theories. Some Suggestions for future research were also raised.</p></div

Description of NASA-TLX 6-dimensional questionnaire (Hart & Staveland, 1988).

<p>Description of NASA-TLX 6-dimensional questionnaire (Hart & Staveland, 1988).</p