Abstract
This article examines the emergence and development in China of the discipline of international organizations law by specifically focusing on the scholarship of Professor Rao Geping, a ...founding figure of the discipline. Rao’s writings are read in light of his personal life and professional career as well as China’s economic and social reforms and its foreign policy. A communitarian, cooperative and legal approach to international organizations emerged as Rao’s choice. International organizations are seen mostly as fora for interstate deliberations and negotiations and are approached mainly from their procedural aspect and channelling function. What has been highlighted is a facilitative, procedural and instrumental conception of international organizations rather than an autonomous, functional or regulatory one. Rao advocates an inclusive approach to international organizations, which tends to include flexible, informal frameworks into the ambit of the study of international organizations. In constructing institutions as forms and fora, Rao’s writings effectively play a double role, translating the liberal, progressive ideas of international organizations into domestic international legal studies and facilitating China’s continuous economic reform and political integration into the international system. Rao’s scholarship presents an instructive example of how a scholar from a semi-periphery country may navigate various tensions and paradoxes behind universal concepts and negotiate their concept of international organizations.
Though sludge foaming often occurs and thus causes serious membrane fouling in membrane bioreactors (MBRs), the fouling mechanisms related with the foaming phenomenon have not been well addressed, ...hindering better understanding and solving foaming problem. In this work, it was interestingly found that, the foulants during the foaming period possessed extremely high specific filtration resistance (SFR) (over 1016 m kg−1) and strong adhesion ability to membrane surface. Chemical characterization showed that the proteins (178.57 mg/L) and polysaccharides (209.21 mg/L) in the foaming sample were about 6.4 times and 5.4 times of those in the supernatant sample, suggesting existence of a mechanism permitting continuous production of these foulants in the MBR during the foaming period. It was revealed that the fouling caused by foams was associated with gel layer filtration process, and the extremely high SFR can be interpreted by chemical potential change in the gel filtration process depicted in Flory-Huggins theory. Meanwhile, analyses by the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory showed that the strong adhesion ability stemmed from the high interaction energy between the foaming foulants and membrane surface. In addition, 16S rDNA gene sequencing identified that the abundance of the foaming related bacteria species in the sludge suspension during the foaming period was more than 10 times of that during the non-foaming period. This study offered new mechanism insights into foaming fouling in MBRs.
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•Foaming foulants had a high specific filtration resistance (SFR) of 1.11 × 1016 m kg−1•There is a mechanism permitting continuous production of foaming foulants in the MBR.•High foaming SFR was related with gel filtration and caused by chemical potential gap.•The strong adhesion ability of foams stemmed from the high interaction energy.•Abundance of foaming related bacteria is 10 times of that during non-foaming period.
Here we report a novel approach to synthesize atomically dispersed uniform clusters via a cage-separated precursor preselection and pyrolysis strategy. To illustrate this strategy, well-defined ...Ru3(CO)12 was separated as a precursor by suitable molecular-scale cages of zeolitic imidazolate frameworks (ZIFs). After thermal treatment under confinement in the cages, uniform Ru3 clusters stabilized by nitrogen species (Ru3/CN) were obtained. Importantly, we found that Ru3/CN exhibits excellent catalytic activity (100% conversion), high chemoselectivity (100% for 2-aminobenzaldehyde), and significantly high turnover frequency (TOF) for oxidation of 2-aminobenzyl alcohol. The TOF of Ru3/CN (4320 h–1) is about 23 times higher than that of small-sized (ca. 2.5 nm) Ru particles (TOF = 184 h–1). This striking difference is attributed to a disparity in the interaction between Ru species and adsorbed reactants.
Metal–organic frameworks (MOFs) have demonstrated great potentials in a variety of important applications. To enhance the inherent properties and endow materials with multifunctionality, the rational ...design and synthesis of MOFs with nanoscale porosity and hollow feature is highly desired and remains a great challenge. In this work, the formation of a series of well‐defined MOF (MOF‐5, FeII‐MOF‐5, FeIII‐MOF‐5) hollow nanocages by a facile solvothermal method, without any additional supporting template is reported. A surface‐energy‐driven mechanism may be responsible for the formation of hollow nanocages. The addition of pre‐synthesized poly(vinylpyrrolidone)‐ (PVP) capped noble‐metal nanoparticles into the synthetic system of MOF hollow nanocages yields the yolk–shell noble metal@MOF nanostructures. The present strategy to fabricate hollow and yolk–shell nanostructures is expected to open up exciting opportunities for developing a novel class of inorganic–organic hybrid functional nanomaterials.
Inorganic–organic hybrids: A series of well‐defined metal–organic frameworks and FeIII‐ICP hollow nanocages (see picture; ICP=infinite coordination polymer) were solvothermally prepared. A surface‐energy‐driven mechanism may be responsible for the formation of these hollow nanocages.
While molecular weight distribution (MWD) is one of the most important properties of soluble microbial products (SMPs), mechanisms underlying effects of MWD of SMPs on membrane fouling have not well ...unveiled. In this study, it was found that, the supernatant of sludge suspension in a membrane bioreactor (MBR) for wastewater treatment can be fractionated into a series of SMPs samples with different molecular weight (MW) fraction. The real gel sample mainly formed by the rejected SMPs on membrane surface had a high specific filtration resistance (SFR) of 1.21 × 1016 m−1 kg−1. The SFR of SMPs samples and the model foulants of polyethylene glycol (PEG) increased with their MW. The change trend of SFR with MW cannot be sufficiently explained by three-dimensional excitation-emission matrix (EMM) and chemical compositions. Tyndall effect analysis indicated that gelating ability of SMPs and PEG in the solution increased with their MW. Scanning electron microscope (SEM) confirmed gel structure changes with the PEG MW. Accordingly, mechanisms based on Carman–Kozeny equation and Flory–Huggins lattice theory were proposed to interpret SFR of SMPs with low and high MW, respectively. Simulating these two mechanistic models on PEG samples resulted in the comparable SFR data to the experimental ones, indicating the correctness and feasibility of the proposed mechanisms. The proposed mechanisms provided in-depth understanding of membrane fouling regarding MW, facilitating to develop effective membrane fouling mitigation strategies.
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•Specific filtration resistance (SFR) of SMPs increased with molecular weight (MW).•Gelating ability of SMPs and PEG in the solution increased with their MW.•Carman–Kozeny equation based mechanism governed SFR of SMPs with low MW.•Flory–Huggins lattice theory well explained SFR of SMPs with high MW.
► Halloysite nanotubes act as a carrier of antibacterial agent for loading copper ions. ► PES UF membranes containing HNTs loaded with copper ions were prepared. ► The membranes showed good ...antibacterial performance against Escherichia coli and S. aureus.
Polyethersulfone ultrafiltration membrane containing halloysite nanotubes loaded with copper ions (Cu2+-HNTs/PES) were prepared via phase inversion method using polyethersulfone (PES) as membrane material and Cu2+-HNTs as an antibacterial agent, which were synthesized by chemical modification of HNTs with silane coupling agent, and then mixed with copper dichloride for complexing copper ions. The morphology and performance of the membranes were characterized by SEM, AFM, TEM, contact angle, and mechanical measurements. The hybrid membranes were shown to be more hydrophilic, with a higher pure water flux. Mechanical test revealed that the mechanical strength of hybrid membranes increased as the addition of Cu2+-HNTs. It was also found that Cu2+-HNTs were dispersed uniformly in the membrane. The antibacterial test indicated that the hybrid membranes showed good antibacterial performance against Gram-negative bacteria (Escherichia coli) and Gram-positive bacteria (Staphylococcus aureus).
Metal‐organic frameworks (MOFs) are potentially useful molecular materials that can exhibit structure flexibilities induced by some external stimuli. Such structure transformations can furnish MOFs ...with improved properties. The shape‐controlled growth of MOFs combined with crystal‐structure transformation is rarely achieved. Herein, we demonstrate the synthesis of hierarchical Zn/Ni‐MOF‐2 nanosheet‐assembled hollow nanocubes (NAHNs) by a facile surfactant‐free solvothermal approach. The unique nanostructures undergo crystal‐structure transformation from Zn/Ni‐MOF‐5 nanocubes to Zn/Ni‐MOF‐2 nanosheets, which is analogous to the dissolution and recrystallization of inorganic nanocrystals. The present synthetic strategy to fabricate isostructural MOFs with hierarchical, hollow, and bimetallic nanostructures is expected to expand the diversity and range of potential applications of MOFs.
Cubed route: A facile surfactant‐free solvothermal approach gives nanostructures that undergo a crystal‐structure transformation from Zn/Ni‐MOF‐5 nanocubes to Zn/Ni‐MOF‐2 nanosheets. The nanosheets retain the cubic shape suggesting that the in situ synthesized nanocubes may act as a template. Immobilization of palladium in the nanosheet structure gives a catalyst for the alkoxycarbonylation of aryl iodides.
Most two-dimensional (2D) covalent organic frameworks (COFs) are non-fluorescent in the solid state even when they are constructed from emissive building blocks. The fluorescence quenching is usually ...attributed to non-irradiative rotation-related or π-π stacking-caused thermal energy dissipation process. Currently there is a lack of guiding principle on how to design fluorescent, solid-state material made of COF. Herein, we demonstrate that the eclipsed stacking structure of 2D COFs can be used to turn on, and tune, the solid-state photoluminescence from non-emissive building blocks by the restriction of intramolecular bond rotation via intralayer and interlayer hydrogen bonds among highly organized layers in the eclipse-stacked COFs. Our COFs serve as a platform whereby the size of the conjugated linkers and side-chain functionalities can be varied, rendering the emission colour-tuneable from blue to yellow and even white. This work provides a guide to design new solid-state emitters using COFs.
Abstract
Transition metal-catalyzed carbonylative reaction with CO gas are among the central task in organic synthesis, enabling the construction of highly valuable carbonyl compound. Here, we show ...an earth-abundant nickel-catalyzed three-component tandem acylzincation/cyclization sequence of allene and alkylzinc reagent with 1 atm of CO under mild conditions. This protocol is featured by broad functional group tolerance with high reaction selectivity, providing a rapid and convenient synthetic method for the construction of diverse fully substituted benzotropone derivatives. Mechanistic studies reveal that the installation of a cyano group tethered to allene moiety enables the high regio- and stereoselectivity of this acylzincation of allene, allowing the selective formation of three consecutive C-C bonds in a highly efficient manner.
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