Temperature-dependent solubility of Rebaudioside A in methanol/ethanol and ethyl acetate mixtures:Experimental measurements and thermodynamic modeling

The equilibrium solubility of Rebaudioside A(Reb A)FormⅡin binary mixtures of methanol/ethanol and ethyl acetate was quantitatively determined within the temperature range of 283.15—328.15 K at ambient pressure.The experimental findings indicate a positive correlation between the solubility of Reb A(FormⅡ)and both the temperature and the methanol/ethanol content in the solvent system.To describe the solubility data,six distinct models were employed:the modified Apelblat equation,theλh model,the combined nearly ideal binary solvent/Redlich—Kister(CNIBS/R—K)model,the van't HoffJouyban-Acree(VJA)model,the Apelblat-Jouyban-Acree(AJA)model,and the non-random two-liquid(NRTL)model.The combined nearly ideal binary solvent/Redlich—Kister model exhibited the most precise fit for solubility in methanol+ethyl acetate mixtures,reflected by an average relative deviation(ARD)of 0.0011 and a root mean square deviation(RMSD)of 12×10^(-7).Conversely,for ethanol+ethyl acetate mixtures,the modified Apelblat equation provided a superior correlation(ARD=0.0014,RMSD=4×10^(-7)).Furthermore,thermodynamic parameters associated with the dissolution of Reb A(FormⅡ),including enthalpy,entropy,and the Gibbs energy change,were inferred from the data.The findings underscore that the dissolution process is predominantly endothermic across the solvent systems examined.Notably,the entropy changes appear to have a significant influence on the Gibbs free energy associated with the dissolution of Reb A(FormⅡ),suggesting that entropic factors may play a pivotal role in the studied systems.

AI in Chemical Engineering: A New Chapter of Innovation

The integration of artificial intelli-gence(AI)into chemical engineering marks a transformative era,redefin-ing traditional methodologies with AI-driven approaches.AI has emerged as a powerful ally in tackling complex problems once considered insur-mountable.As chemical engineering grapples with increasingly complex systems and stringent sustainability targets,AI sets the stage for a new generation of solutions.

客体溶剂导向策略构筑异构的金属有机框架材料实现二氧化碳和甲烷的动力学分离

利用吸附分离技术实现二氧化碳和甲烷的分离是提高天然气品质的一种有效手段。然而,基于热力学分离的吸附剂对二氧化碳往往表现出很强的亲和力,因此再生过程会产生巨大的能耗。相较而言,尽管精准调控吸附剂孔径以实现吸附质扩散速率的巨大差异仍具有巨大挑战,动力学分离技术仍是变压吸附(PSA)过程的首选。本文报道了一种用于在亚埃尺度精准调控吸附剂孔径的客体溶剂导向策略,实现了二氧化碳和甲烷的高效动力学分离。基于4,4-(六氟异丙基亚甲基)-双(苯甲酸)和双核铜的轮桨型结构单元,我们构筑了一系列异构的金属有机框架材料。结果表明,得益于周期性扩张和收缩的孔道以及理想的孔径尺寸,CuFMOF·CH_(3)OH(CuFMOF-c)能够有效地捕获二氧化碳并阻碍甲烷的扩散,从而表现出优异的动力学分离性能,其具有极高的动力学选择性(273.5)和平衡-动力学综合选择性(64.2)。分子动力学(MD)模拟阐明了分离机制,固定床穿透实验验证了材料优异的分离性能。

Hybridization of metal–organic framework and monodisperse spherical silica for chromatographic separation of xylene isomers

Metal–organic frameworks(MOFs) packed in the column have been a promising candidate as the stationary phase for high performance liquid chromatography(HPLC). However, the direct packing of irregular MOF powder could raise some problems like high back pressure and low column efficiency in the HPLC separation. In this work, UiO-66 capable of separating xylenes was supported effectively on the surface of the monodisperse spherical silica microspheres by one-pot method. The hybridization of Ui O-66 and silica microspheres(termed UiO-66@SiO2 shell–core composite) was prepared by stirring the suspension of the precursors of Ui O-66 and\\COOH terminated silica in the N,N-dimethylformamide with heating. The shell–core composite material UiO66@SiO2 was characterized by SEM, TEM, PXRD and FTIR. Then, it was used as a packing material for the chromatographic separation of xylene isomers. Xylene isomers including o-xylene, m-xylene and p-xylene were efficiently separated on the column with high resolution and good reproducibility. Moreover, the Ui O-66@SiO2 shell–core composites packed column still remained reverse shape selectivity as Ui O-66 possessed, and the retention of xylenes was probably ascribed to the hydrophobic effect between analytes and the aromatic rings of the Ui O-66 shell. The Ui O-66@SiO2 shell–core composites obtained in this study have some potential for the separation of structural isomers in HPLC.

Highly efficient and anti-poisoning single-atom cobalt catalyst for selective hydrogenation of nitroarenes

Developing non-precious metal catalysts to selectively reduce functionalized nitroarenes with high efficiency is urgently desirable for the production of value-added amines.Herein,we report a novel,efficient,anti-poisoning single-atom cobalt catalyst(Co-NAC)for the highly selective hydrogenation of the nitro to amino group for nitroarenes baring various functional groups,including vinyl,cyano,and halogen.Using a combination of structure characterization techniques,we have confirmed that the cobalt species are predominantly present in the form of four-coordinated Co single sites anchored on nitrogen-assembly carbon(NAC)as the ordered mesoporous support.Co-NAC catalysts enable the full conversion and>99%selectivity with molecular H2 as a green reductant under mild conditions(80℃,2 MPa H2).As for the selective hydrogenation of 3-nitrostyrene,Co-NAC catalyst affords high catalytic productivity(19.7 h-1),which is superior to the cobalt nanoparticles(NPs)catalysts and most of the recently reported Co-based catalysts.This is attributed to the highly accessible atomically-dispersed Co active sites,the high surface area with ordered-mesoporous morphology and the prominent high content of nitrogen dopants.Notably,Co-NAC catalyst displays resistance towards sulfur-containing poisons(20 equivalents)and strong non-oxidizing acid(8 M),showing great potential for continuous application in the chemical industry.

多极性位点的杂化氢键有机框架吸附分离CO_(2)/CH_(4)

氢键有机框架(HOFs)是极具研究价值的新型多孔材料,但稳定、永久多孔且富含功能位点的HOFs的构筑难题制约了其在气体吸附分离领域的应用.本文采用具有轮桨立体构型和多氢键位点的金属-核碱基构造体构筑了一类稳定的微孔杂化HOFs材料(HOF-ZJU-201、HOF-ZJU-202和HOF-ZJU-203),框架内的无机阴离子、氨基以及电荷差异性分布孔道作为多重极性位点实现了CO_(2)的选择性吸附和CO_(2)/CH_(4)的吸附分离.在298 K和1 bar(1 bar=105 Pa)条件下,杂化HOFs材料的CO_(2)吸附量为2.31~3.35 mmol/g,对CO_(2)/CH_(4)(50/50,v:v)的分离选择性为7.3~9.0.通过色散矫正的密度泛函理论计算和Hirshfeld表面分析明确了杂化HOFs材料通过氢键、静电偶极作用以及范德华力选择性捕获CO_(2)的作用机理.固定床穿透实验进一步验证了杂化HOFs材料对CO_(2)/CH_(4)的动态吸附性能,能够从等摩尔二元混合气中直接获得纯度99.9%的甲烷,具有低浓度甲烷气高效提浓的应用潜力.杂化HOFs材料良好的空气、水汽、热稳定性以及优异的循环稳定性和化学稳定性使其具备工业化应用潜力.

芯片制造电子电镀表界面科学基础——第341期“双清论坛”综述

电子电镀作为芯片制造中唯一能够实现纳米级电子逻辑互连的技术方法,是国家高端制造战略安全的重要支撑.本文基于国家自然科学基金委员会第341期“双清论坛”,针对我国在芯片制造电子电镀领域的重大需求,梳理了芯片制造电子电镀表界面科学基础的研究现状、发展趋势及面临的挑战,凝炼了该研究领域急需关注和亟待解决的重要基础科学问题,探讨了今后5~10年的科学基金重点资助方向,为国家相关政策的总体布局提供有效的参考建议.

超微孔碳吸附剂实现天然气中丙烷和乙烷的高选择性提取

轻烃混合物分离以及从天然气中提取C3H8和C2H6对天然气纯化及劣质天然气升级意义重大.微孔碳吸附剂在轻烃分离中潜力巨大,然而构筑孔径均一的超微孔从而增强分离选择性仍是巨大挑战.在本文中,我们采取无活化剂热解法制备了一系列孔径均一(5.2到5.3?)的聚偏二氯乙烯树脂(PVDC)衍生的超微孔碳吸附剂.与已报道的吸附剂相比,优选的C-PVDC-800对C3H8/CH4及C2H6/CH4在298 K和1.0 bar下表现出更高的理想吸附溶液理论(IAST)选择性(分别为3387和75),对C3H8/CH4具有最高的Henry系数选择性(369).此外,C-PVDC-800在低压下对C3H8和C2H6具有极高的吸附量.更重要的是,该材料对所有气体分子都实现了快速的动力学吸附,有利于应用于固定床吸附过程.固定床穿透实验及循环测试进一步证实了该材料从天然气中选择性提取C3H8和C2H6的优异性能.

Boosting xenon adsorption with record capacity in microporous carbon molecular sieves

Xenon/krypton(Xe/Kr)separation is an important task in industry,yet it remains challenging to develop adsorbents with high Xe/Kr selectivity and adsorption capacity of Xe,especially at low partial pressures.Herein,we report a series of microporous carbon molecular sieves(CMSs)for Xe/Kr separation.Those materials have ideal bimodal pore size distributions that not only provide substantial space for the accommodation of gas molecules,but also allow selective diffusion of gas molecules.Additionally,the carbon frameworks decorated with polar oxygen-containing functional groups afford higher affinity for Xe than Kr,which is proven by density functional theory(DFT)calculations and charge density difference analysis.The optimal CPVDC-700 exhibits a high selectivity of Xe/Kr and,more importantly,a record-high uptake of Xe(2.93 mmol g^(-1))at 0.2 bar and298 K,which is the highest among all the reported carbon adsorbents.Breakthrough experiments confirm the excellent performance of such CMSs for Xe/Kr separation,and the dynamic adsorption uptake of Xe and productivity of high-purity Kr are calculated to be 2.91 mmol g^(-1)and 208 m L g^(-1)(9.29 mmol g^(-1)),respectively,which also set up a new benchmark for Xe/Kr separation of carbon adsorbents.

Pd-Ni nanoparticles supported on titanium oxide as effective catalysts for Suzuki-Miyaura coupling reactions

We have successfully prepared a series of Pd- Ni/TiO2 catalysts by a one-step impregnation-reduction method. Among these catalysts with different compositions of Ni and Pd, the one with the Ni：Pd ratio of 2.95 showed the best activity. Small monodispersed Pd-Ni bimetallic nanoparticles were loaded on the surface of titanium oxide nanopowder as confirmed with TEM and EDS mapping. The XPS analysis demonstrated that Pd exists as 31% Pd（II） species and 69% Pd（0） species and all nickel is Ni（II）. The prepared Pd-Ni/TiO2 exhibited enhanced catalytic activity compared to an equal amount of Pd/TiO2 for Suzuki-Miyaura reactions together with excellent applicability and reusability.

Room-temperature hydrogenation of halogenated nitrobenzenes over metal-organic-framework-derived ultra-dispersed Ni stabilized by N-doped carbon nanoneedles

Ultra-dispersed Ni nanoparticles(7.5 nm)on nitrogen-doped carbon nanoneedles(Ni@NCNs)were prepared by simple pyrolysis of Ni-based metal–organic-framework for selective hydrogenation of halogenated nitrobenzenes to corresponding anilines.Two different crystallization methods(stirring and static)were compared and the optimal pyrolysis temperature was explored.Ni@NCNs were systematically characterized by wide analytical techniques.In the hydrogenation of p-chloronitrobenzene,Ni@NCNs-600(pyrolyzed at 600°C)exhibited extraordinarily high performance with 77.9 h^(–1)catalytic productivity and>99%p-chloroaniline selectivity at full p-chloronitrobenzene conversion under mild conditions(90°C,1.5 MPa H2),showing obvious superiority compared with reported Ni-based catalysts.Notably,the reaction smoothly proceeded at room temperature with full conversion and>99%selectivity.Moreover,Ni@NCNs-600 afforded good tolerance to various nitroarenes substituted by sensitive groups(halogen,nitrile,keto,carboxylic,etc.),and could be easily recycled by magnetic separation and reused for 5 times without deactivation.The adsorption tests showed that the preferential adsorption of–NO2 on the catalyst can restrain the dehalogenation of p-chloronitrobenzene,thus achieving high p-chloroaniline selectivity.While the high activity can be attributed to high Ni dispersion,special morphology,and rich pore structure of the catalyst.

A robust ethane-trapping metal-organic framework for efficient purification of ethylene

Owing to the similar physicochemical properties between ethane(C_(2)H_(6))and ethylene(C_(2)H_(4)),obtaining polymerization-grade C_(2)H_(4)(≥99.95%pure)is still a tricky problem in the petrochemical industry.Here,we report a robust scandium-based metalorganic framework(Sc BPDC),which is connected by oxygen-rich phenyl ligand with exceptionally high thermal stability(up to873 K)and capacity of C_(2)H_(6)(4.94 mmol/g at 100 k Pa and 283 K),exhibiting superior separation performance of C_(2)H_(6)/C_(2)H_(4) mixture(the IAST selectivity is up to 1.7 at 283 K).Importantly,Sc BPDC can produce 8.96 L/kg C_(2)H_(4) with≥99.99%purity while the C_(2)H_(4)/C_(2)H_(6)(50:50,v/v)as the mixture injection and the low isosteric heat of Sc BPDC(16.4 k J/mol for C_(2)H_(6))validates the facility of adsorbent regeneration.Furthermore,theoretical calculations demonstrate the C_(2)H_(6) molecules are trapped in the nonpolar pore surface via C–H···πand C–H···O interactions between multiple hydrogen atoms of C_(2)H_(6) and the host framework.

Porous Hydrogen-Bonded Frameworks Assembled from Metal-Nucleobase Entities for Xe/Kr Separation

It is challenging to obtain high-purity xenon(Xe)and krypton(Kr)from the by-products of the air separation process due to their similar atom size and physical properties.Adsorption using porous materials such as metal–organic frameworks(MOFs)has been considered a promising technology to separate Xe/Kr.Herein,we report two novel isostructural ionic supramolecular MOFs(SMOFs;SMOF-PFSIX-1 and SMOF-AsFSIX-1),in which inorganic anions(PF_(6)^(−)or AsF_(6)^(−))and cationic metal–organic entities have self-assembled through hydrogen bonds to give three-dimensional pore channels.The two kinds of SMOFs can efficiently separate Xe/Kr with ideal adsorbed solution theory(IAST)selectivity values of 6.9 and 6.7 under 298 K and 1.0 bar,respectively.The breakthrough experiments further confirm their industrial application potential.The grand canonical Monte Carlo(GCMC)and density functional theory(DFT)calculations revealed that there are multiple adsorptive sites to capture the Xe atom,and the affinity between Xe and frameworks can be attributed to the inorganic anions and amino groups on the ligands.To the best of our knowledge,this was the first report of using SMOFs for Xe/Kr separation,and we proposed a new strategy for Xe/Kr separation based on the synergistic effect of amino and inorganic anions.

Hydrogen-bonded metal-nucleobase frameworks for highly selective capture of ethane/propane from methane and methane/nitrogen separation

The separation of light hydrocarbons,including C_(2)H_(6)and C_(3)H_(8),is essential to natural gas upgrading.Meanwhile,N_(2)removal from CH_(4)is also crucial to concentrating low-quality coalbed methane,but the adsorption process is challenging because of the close kinetic diameter.This work reports two hydrogen-bonded metal-nucleobase frameworks(HOF-ZJU-201 and HOF-ZJU202)capable of efficiently separating C_(3)H_(8)/CH_(4),C_(2)H_(6)/CH_(4),and CH_(4)/N_(2).Due to strong affinity for C_(3)H_(8)and C_(2)H_(6),the lowpressure capacity for C_(3)H_(8)(5 kPa)and C_(2)H_(6)(10 kPa)of HOF-ZJU-201a exceeds most adsorbents.The ideal adsorbed solution theory(IAST)selectivity of C_(3)H_(8)/CH_(4)and C_(2)H_(6)/CH_(4)is 119 and 45 at ambient conditions.According to density functional theory calculations,surface polarization environments formed by electron-rich anions and electron-deficient purine heterocyclic rings contribute to the selective capture of C_(3)H_(8)and C_(2)H_(6)with greater polarizability.Furthermore,the high CH_(4)adsorption capacity(1.73 mmol/g for HOF-ZJU-201a and 1.50 mmol/g for HOF-ZJU-202a at 298 K and 1.0 bar)and excellent CH_(4)/N_(2)selectivity(6.0 for HOF-ZJU-201 at 298 K),as well as dynamic breakthrough experiments of binary CH_(4)/N_(2)gas mixture implied their efficacy in the concentration of low-quality coalbed methane.