Cholesterol-Mediated Anchoring of Phospholipids onto Proteinosomes for Switching Membrane Permeability.

Modulated membrane functionalization is a necessary and overarching step for hollow microcompartments toward their application as nanoreactors or artificial cells. In this study, we show a way to generate phospholipid hybrid proteinosomes that could show superposed virtues of liposomes and proteinosomes. In comparison to pure proteinosomes, both the membrane fluidity and permeability are improved obviously after forming the phospholipid hybrid proteinosomes. Specifically, the integration of phospholipids also endows the hybrid proteinosomes demonstrating a stepwise release of the encapsulants of FITC-dextran (70 and 150 kDa) triggered sequentially by phospholipase and protease, and then a modulated cascaded enzymatic reaction between two different populations of proteinosomes are achieved. Therefore, it is anticipated that such constructed phospholipid hybrid proteinosomes could be employed as an improved microcompartmental model for further advanced artificial cell design toward achieving logic signal communication within the various artificial cellular populations as well as potential applications in the field of microreactors.

Amino-assisted AHMT anchored on graphene oxide as high performance adsorbent for efficient removal of Cr(VI) and Hg(II) from aqueous solutions under wide pH range.

The adsorbents with high adsorption capacity for simultaneously removing Cr(VI) and Hg(II) from aqueous solutions under broad working pH range are highly desirable but still extremely scarce. Here, a novel adsorbent with multidentate ligands was facilely fabricated by covalently bonding 4-amino-3-hydrazino-5-mercapto- 1,2,4-triazole on graphene oxide via the Schiff's base reaction. The maximum adsorption capacities of Cr(VI) and Hg(II) on the current adsorbent were 734.2 and 1091.1 mg/g, which were 14.36 and 5.61 times higher than that of the pure graphene oxide, respectively, exceeding those of most adsorbents previously reported. More interestingly, Cr(VI) and Hg(II) concentrations were decreased from 2 mg/L to 0.0001 mg/L for Hg(II) and 0.004 mg/L for Cr(VI), far below the WHO recommended threshold for drinking water. Moreover, the adsorbent shows an excellent performance for simultaneous removal of Cr(VI) and Hg(II) with more than 99.9% and 98.6% removal efficiencies in aqueous solutions. Finally, the adsorbent was successfully applied in dealing with the real industrial effluent, implying huge potential in industrial application. This work offers a new possibility for the removal of the metallic contaminants by rational designing target groups and ligands.

Cross-linked sulfydryl-functionalized graphene oxide as ultra-high capacity adsorbent for high selectivity and ppb level removal of mercury from water under wide pH range.

It is highly desirable but remains extremely challenging to develop a facile strategy to prepare adsorbent for dealing with heavy metal pollution in water. Here, we report a facile approach for preparing sulfydryl-functionalized graphene oxide (S-GO) by cross-linking method with an unprecedented adsorption capacity and ultrahigh selectivity for efficient Hg(II) removal. The adsorbents exhibit a prominent performance in capturing Hg(II) from wastewater with a record-high adsorption capacity of 3490 mg/g and rapid kinetics to reduce Hg(II) contaminants below the discharge standard of drinking water (2 ppb) within 60 min under a wide pH range even in the coexistent of other interfering metal ions. In addition, the adsorbents can be also easily recycled and reused multiple times with no apparent decline in removal efficiency. Considering the broad diversity, we developed also a magnetic Fe3O4/S-GO adsorbent by a simple chemical cross-linking reaction to achieve rapid separation of S-GO from their aqueous solution. In addition, the adsorbents were successfully applied in dealing with the practical industrial wastewater. The results indicate the potential of rationally designed sulfydryl-functionalized graphene oxide for high performance Hg(II) removal.

Highly efficient and ultrafast removal of Cr(VI)in aqueous solution to ppb level by poly(allylamine hydrochloride) covalently cross-linked amino-modified graphene oxide.

We herein report a facile strategy to prepare poly(allylamine hydrochloride) cross-linked amino-modified graphene oxide (PAH-ASGO) by Schiff-base reactions. The resulting PAH-ASGO exhibited a maximum adsorption capacity of 373.1 mg/g for Cr(VI), which was nearly 9 times higher than that of pure graphene oxide, exceeding that of most GO-based materials previously reported. More significantly, PAH-ASGO can effectively diminish the Cr(VI) concentration from 9.9 mg/L to the extremely low level of 0.004 mg/L within 10 s, far below the maximum allowable level of Cr(VI) (0.05 mg/L) in drinking water. In addition, the adsorbents still displayed excellent removal efficiency of 91.8% after 10 cycles. Considering the broad diversity, we developed also a magnetic PAH-ASGO/Fe3O4 adsorbent by a simple cross-linking reaction to achieve rapid separation of PAH-ASGO from their aqueous solution. Finally, the PAH-ASGO was successfully utilized to treat the actual industrial effluent.

Refinement of pore size at sub-angstrom precision in robust metal-organic frameworks for separation of xylenes.

The demand for xylenes is projected to increase over the coming decades. The separation of xylene isomers, particularly p- and m-xylenes, is vital for the production of numerous polymers and materials. However, current state-of-the-art separation is based upon fractional crystallisation at 220 K which is highly energy intensive. Here, we report the discrimination of xylene isomers via refinement of the pore size in a series of porous metal-organic frameworks, MFM-300, at sub-angstrom precision leading to the optimal kinetic separation of all three xylene isomers at room temperature. The exceptional performance of MFM-300 for xylene separation is confirmed by dynamic ternary breakthrough experiments. In-depth structural and vibrational investigations using synchrotron X-ray diffraction and terahertz spectroscopy define the underlying host-guest interactions that give rise to the observed selectivity (p-xylene < o-xylene < m-xylene) and separation factors of 4.6-18 for p- and m-xylenes.

Amino-functionalized graphene oxide-supported networked Pd-Ag nanowires as highly efficient catalyst for reducing Cr(VI) in industrial effluent by formic acid.

Cr(VI) pollution in wastewater has increasingly become a global environmental problem owing to its acute toxicity. Herein, we present the one-pot procedure for preparing the amino-functionalized (-NH2) graphene oxide (GO-) supported networked Pd-Ag nanowires by co-reduction growth in polyol solution, which show the highly efficient catalytic performance with the excellent cycling stability for the catalytic Cr(VI) reduction by formic acid as an in-situ source of hydrogen at room temperature. The electron transfer from Ag and amino to Pd increases the electron density of Pd, which enhances the catalytic formic acid decomposition and subsequent the catalytic Cr(VI) reduction. The catalytic reduction rate constant of Pd3Ag1/GO-NH2 is determined to be 0.0768 min-1, which is much superior to the monometallic Pd/GO-NH2 and Pd3Ag1/GO. This study provides a novel strategy to develop catalysts for the catalytic reduction of Cr(VI) to Cr(III) in the industrial effluent using formic acid as an in-situ source of hydrogen.

A green approach for enhancing the hydrophobicity of UiO-66(Zr) catalysts for biodiesel production at 298 K.

Recently, the incorporation of hydrophobicity on the surface of UiO-66(Zr) has received much attention due to the deactivation of hydrophilic active sites of UiO-66(Zr) upon water adsorption. In this work, we report UiO-66(Zr) catalysts with an assortment of surface hydrophobicities fabricated by the solvent-free method to elucidate the impact of the environment framing Lewis acid sites on their catalytic activity in the production of fatty acid methyl ester (biodiesel) via the esterification of fatty acids at room temperature with high selectivity (100%) and good recyclability. A detailed structural analysis of the materials by N2 sorption, FT-IR, SEM, XRD, water contact angle measurement, dynamic liquid scattering (DLS), NMR and TGA revealed the fabrication of stearic acid-grafted UiO-66(Zr) catalysts (10SA/UiO-66) with fine particle size and a highly hydrophobic network. 10SA/UiO-66(Zr) with enhanced hydrophobicity exhibited superior catalytic performance in the esterification of a fatty acid with a long alkyl chain compared with conventional solid acid catalysts and even liquid acid catalysts. Detailed kinetic studies corroborated that the adsorption of lipophilic acids at the Lewis acid sites besides the enhancement of wettability between the reactants was facilitated by the hydrophobic environment, thus significantly motivating the esterification reaction at room temperature. Furthermore, 10SA/UiO-66(Zr) showed good catalytic activity in the esterification of oleic acid in the presence of water (∼10% in the light of acid weight).

One-pot synthesis of magnetic graphene oxide composites as an efficient and recoverable adsorbent for Cd(II) and Pb(II) removal from aqueous solution.

It is extremely desirable but challenging to develop a facile synthesis method to directly prepare reusable and longtime stable magnetic graphene oxide (GO) adsorbent. Here, a new approach to prepare a magnetic GO for removing the heavy metal ions is reported by using n-Propyltrimethoxysilane (NPTS) as a cross-coupling agent to connect Fe3O4/SiO2 and GO. The as-prepared magnetic GO can be separated quickly from their aqueous solution by the permanent magnet and also exhibited excellent adsorption performance for Cd(II) and Pb(II) with maximum adsorption capacities for Cd(II) and Pb(II) to 128.2 and 385.1 mg/g under neutral conditions, respectively. The presence of other ions such as Na(I) and K(I), had little influence on the Cd(II) and Pb(II) removal efficiency. Moreover, the as-prepared Fe3O4/SiO2-GO adsorbents can be recycled and exhibited good reproducibility. Thus, the magnetic GO adsorbents are effective materials for the removal of heavy metal ions and thus could offer a new platform for water cleanup.

Boosting Catalytic Performance of Metal-Organic Framework by Increasing the Defects via a Facile and Green Approach.

The control of defects in crystalline materials has long been of significance since the defects are correlated with the performances of the materials. Yet such control remains a challenge for metal-organic frameworks (MOFs), which are usually well-crystallized under hydro-/solvothermal conditions. In this contribution, we demonstrate for the first time how to increase the defects of MOF via a facile and green approach as exemplified in the context of solvent-free synthesis of UiO-66(Zr). Such increase of defects leads to drastic enhancement of catalysis performance when compared to UiO-66(Zr) prepared from conventional hydro-/solvothermal synthesis. Our work therefore not only opens a new door for boosting the catalytic activities of MOFs but also contributes a new approach to control the defects in crystalline materials for various applications.

Enhancement of Oxidative Desulfurization Performance over UiO-66(Zr) by Titanium Ion Exchange.

Oxidative desulfurization is considered to be one of the most promising methods for producing ultra-low-sulfur fuels because it can effectively remove refractory sulfur-containing aromatic compounds under mild conditions. In this work, the oxidative desulfurization performance over UiO-66(Zr) is greatly enhanced by Ti ion exchange. This strategy is not only efficient for UiO-66(Zr) with crystal defects but also for UiO-66(Zr) with high crystallinity. In particular, the performance of UiO-66(Zr) with high crystallinity in the oxidative desulfurization of dibenzothiophene can be improved more than 11-fold, which can be mainly attributed to the introduction of active Ti sites.

Inserting CO2 into Aryl C-H Bonds of Metal-Organic Frameworks: CO2 Utilization for Direct Heterogeneous C-H Activation.

Described for the first time is that carbon dioxide (CO2 ) can be successfully inserted into aryl C-H bonds of the backbone of a metal-organic framework (MOF) to generate free carboxylate groups, which serve as Brønsted acid sites for efficiently catalyzing the methanolysis of epoxides. The work delineates the very first example of utilizing CO2 for heterogeneous C-H activation and carboxylation reactions on MOFs, and opens a new avenue for CO2 chemical transformations under mild reaction conditions.

Metal-organic framework based upon the synergy of a Brønsted acid framework and Lewis acid centers as a highly efficient heterogeneous catalyst for fixed-bed reactions.

We report a strategy of combining a Brønsted acid metal-organic framework (MOF) with Lewis acid centers to afford a Lewis acid@Brønsted acid MOF with high catalytic activity, as exemplified in the context of MIL-101-Cr-SO3H·Al(III). Because of the synergy between the Brønsted acid framework and the Al(III) Lewis acid centers, MIL-101-Cr-SO3H·Al(III) demonstrates excellent catalytic performance in a series of fixed-bed reactions, outperforming two benchmark zeolite catalysts (H-Beta and HMOR). Our work therefore not only provides a new approach to achieve high catalytic activity in MOFs but also paves a way to develop MOFs as a new type of highly efficient heterogeneous catalysts for fixed-bed reactions.

Investigation of prototypal MOFs consisting of polyhedral cages with accessible Lewis-acid sites for quinoline synthesis.

A series of prototypal metal-organic frameworks (MOFs) consisting of polyhedral cages with accessible Lewis-acid sites, have been systematically investigated for Friedländer annulation reaction, a straightforward approach to synthesizing quinoline and its derivatives. Amongst them MMCF-2 demonstrates significantly enhanced catalytic activity compared with the benchmark MOFs, HKUST-1 and MOF-505, as a result of a high-density of accessible Cu(II) Lewis acid sites and large window size in the cuboctahedral cage-based nanoreactor of MMCF-2.

Microporous magnesium and manganese formates for acetylene storage and separation.

Acetylene sorption of microporous metal formates M(HCOO)2 (M = Mg and Mn) was investigated. Measurements of acetylene sorption at 196, 275, and 298 K showed a Type I isotherm with quick saturation at low pressures, and 50-75 cm3 g(-1) uptake at 1.0 atm. The single-crystal X-ray structure analysis of the acetylene-adsorbed metal formates revealed that acetylene molecules occupy two independent positions in the zigzag channels of the frameworks with a stoichiometry of M(HCOO)2 x 1/3C2H2, which is consistent with the gas sorption experiments. No specific interaction except van der Waals interactions between the adsorbed acetylene molecules and the walls of the frameworks was found. Sorption properties of other gases, including CO2, CH4, N2, O2, and H2, were also investigated. When the temperature was increased to 298 K, the amount of adsorbed acetylene was still above 60 cm3 g(-1) for Mg(HCOO)2 and 50 cm3 g(-1) for Mn(HCOO)2, whereas the uptake of other gases decreased substantially. The microporous metal formates may thus be useful not only for the storage of acetylene but also its separation from other gases at room or slightly higher temperatures.

Neopentane and solid acids: direct hydron exchange before cracking.

The hydrogen/deuterium exchange reaction of 2,2-dimethylpropane (neopentane) over D(2)O-exchanged zeolites (MOR, FAU, BEA, MFI) using a batch recirculation reactor was studied by means of gas chromatography coupled with mass spectrometer. In the temperature range 473-573 K, H/D exchange proceeds without side reaction such as cracking at short contact times. Indeed the C-H bond has appeared favorably involved in the activation of neopentane compared to the less accessible C-C bond. The transition state allowing hydron exchange is most likely a carbonium species (pentacoordinated carbon) as in the case of the H/D exchange between methane and solid acid. The activation energies of the H/D exchange between neopentane and zeolites are the same for all zeolites indicating a common carbonium ion type transition state. On the basis of previous results in the case of the exchange between methane and liquid superacids, the deuterium exchange rates in neopentane were tentatively related to the acidity of the solids. However the order of activity MOR > MFI > BEA > FAU seems to be related to the size of the pores, which may suggest the involvement of a confinement effect in the zeolites cavities. Moreover we found that H/D exchange takes also place between neopentane and deuterated sulfated zirconia (SZ) emphasizing its strong acidity.

Solvent-free preparation of nanosized sulfated zirconia with Brønsted acidic sites from a simple calcination.

Nanosized sulfated zirconia with Brønsted acidic sites has been prepared by a simple calcination in the absence of any solvent. XRD patterns reveal that the sulfated zirconia mainly consists of tetragonal crystalline zirconia with average size of about 7 nm, which is further confirmed by TEM images. N2 adsorption data show that the nanosized sulfated zirconia has high surface area (165-193 m2/g) and exhibits uniform pore distribution aggregated by zirconia nanoparticles. IR spectra of samples show that the sulfur species in the nanosized sulfated zirconia is a little different from that in conventional sulfated zirconia. Furthermore, IR spectra of adsorbed pyridine indicate that the nanosized sulfated zirconia contains relatively more Brønsted acidic sites than conventional sulfated zirconia. Catalytic tests show that the nanosized sulfated zirconia exhibits much higher activity than conventional sulfated zirconia in catalytic esterification of cyclohexanol with acetic acid.