Yingjie Zhou

Sulfonic acid-functionalized α-zirconium phosphate single-layer nanosheets as a strong solid acid for heterogeneous catalysis applications.

Solid acids have received considerable attention as alternatives to traditional corrosive and hazardous homogeneous acids because of their advantages in practical applications, including their low corrosion of equipment and high catalytic activity and recyclability. In this work, a strong solid acid was prepared by anchoring thiol group terminated chains on layered α-zirconium phosphate (ZrP) single-layer nanosheets, followed by oxidation of thiol groups to form sulfonic acid groups. The obtained solid acids were thoroughly characterized and the results proved that sulfonic acid group terminated chains were successfully grafted onto the ZrP nanosheets with a high loading density. Such a strong solid acid based on inorganic nanosheets can be well-dispersed in polar solvents, leading to high accessibility to the acid functional groups. Meanwhile, it can be easily separated from the dispersion system by centrifugation or filtration. The strong solid acid can serve as an effective heterogeneous catalyst for various reactions, including the Bayer-Villiger oxidation of cyclohexanone to ε-caprolactone in the absence of organic solvents.

Titanium incorporated with UiO-66(Zr)-type Metal–Organic Framework (MOF) for photocatalytic application

A UiO-66-type metal–organic framework (MOF) fabricated with titanium was successfully prepared via a facial modified post-grafting method. The as-prepared samples were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), ultraviolet-visible adsorption spectroscopy (UV-vis), and photoluminescence spectroscopy (PL) techniques. The introduction of titanium enhanced the optical properties of UiO-66 via the formation of oxo-bridged hetero-Zr–Ti clusters, but led to a sacrifice in crystallinity. The removal of methylene blue (MB) over these samples could be attributed to the dual function of the adsorption and photo-degradation mechanisms. The highest MB removal efficiency of 87.1% was achieved over UiO-66(1.25Ti) under simulated sun-light irradiation.

In-Situ Fabrication of Graphene Oxide Hybrid Ni-Based Metal–Organic Framework (Ni–MOFs@GO) with Ultrahigh Capacitance as Electrochemical Pseudocapacitor Materials

This paper reports a series of novel Ni-based metal-organic framework (Ni-MOFs) prepared by a facile solvothermal process. The synthetic conditions have great effects on the Ni-MOFs morphologies, porous textures, and their electrochemical performance. Improved capacitance performance was successfully realized by the in-situ hybrid of Ni-MOFs with graphene oxide (GO) nanosheets (Ni-MOFs@GO). The pseudocapacitance of ca. 1457.7 F/g for Ni-MOFs obtained at 180 °C with HCl as the modulator was elevated to ca. 2192.4 F/g at a current density of 1 A/g for the Ni-MOFs@GO with GO contents of 3 wt %. Additionally, the capacitance retention was also promoted from ca. 83.5% to 85.1% of its original capacitance at 10 A/g even after 3000 cycles accordingly. These outstanding electrochemical properties of Ni-based MOF materials may be related to their inherent characteristics, such as the unique flower-like architecture and fascinating synergetic effect between the Ni-MOFs and the GO nanosheets.

Novel Cu–Fe bimetal catalyst for the formation of dimethyl carbonate from carbon dioxide and methanol

A novel Cu–Fe bimetal supported catalytic system was prepared and applied to the direct dimethyl carbonate (DMC) formation from methanol and CO2. The prepared catalysts were characterized by means of temperature-programmed reduction (TPR), X-ray powder diffraction (XRD), laser Raman spectra (LRS), X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (TPD). Metallic Cu, Fe and oxygen deficient Fe2O3−x (0 < x < 3) were formed during the reduction and activation step. The supported Cu–Fe bimetal catalysts exhibited good catalytic activity and high stability for the direct DMC formation. Under the reaction conditions at 120 °C and 1.2 MPa with space velocity of 360 h−1, the highest methanol conversion of 5.37% with DMC selectivity of 85.9% could be achieved. The high catalytic performance of the Cu–Fe bimetal catalysts in the DMC formation could be attributed to the interaction of base sites functioned by metallic Cu and Fe with acid sites provided by oxygen deficient Fe2O3−x (0 < x < 3) in the activation of methanol and CO2. The moderate concentration balance of acid and base sites was in favor of DMC formation.

Designing Supported Ionic Liquids (ILs) within Inorganic Nanosheets for CO2 Capture Applications

A new methodology was developed for the immobilization of ionic liquids (ILs) on α-zirconium phosphate (ZrP) and montmorillonite (MMT) single-layer nanosheets via a facile coassembly process. The coassembled inorganic nanosheet/1-n-butyl-3-methylimidazolium chloride (BMIMCl) hybrids were systematically characterized. The results showed that the ILs were successfully assembled with ZrP or MMT single-layer nanosheets to form an intercalated structure. The inorganic nanosheet/IL hybrids can serve as efficient CO2 absorbents. The CO2 sorption of BMIMCl could be made up to 21 times more efficient because of the high exposure of the functional groups of BMIMCl in the coassembled hybrids. CO2 was physically absorbed by the hybrids with a slow equilibrium time at lower temperatures, whereas higher temperatures allowed for faster diffusion and chemical absorption of CO2. The best CO2 capture capacities of the hybrids were 0.73 mmol/g at 60 °C for ZrP/BMIMCl and 0.42 mmol/g at 70 °C for MMT/BMIMCl.

Titanium functionalized α-zirconium phosphate single layer nanosheets for photocatalyst applications

Titanium species were immobilized on α-ZrP nanosheets (ZrP–Ti) using a modified post-grafting method. The obtained ZrP–Ti composites were characterized via Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), ultraviolet-visible (UV-vis) absorption spectroscopy, photoluminescence spectroscopy (PL), and scanning electron microscopy (SEM). Titanium species in the form of TiO2−x clusters with an average particle size of 2–5 nm were grafted on α-ZrP nanosheets via chemical bonding with P element. These ZrP–Ti composites could be well dispersed in polar solvents to ensure that the TiO2−x clusters bonded on both faces of the nanosheets were accessible. The ZrP–Ti composites presented enhanced visible-light absorption properties compared with that of pure TiO2. These features allowed them to exhibit better photocatalytic activities for the photodegradation of methylene blue (MB) under solar irradiation. The TiO2−x clusters tended to aggregate into anatase phase TiO2 when the molar ratio of P/Ti exceeded 1 : 1, and this reversed the advantage in their photocatalytic activities. The best MB degradation efficiency of 100% with the apparent rate constant of 0.054 min−1 was achieved over the ZrP–Ti composite with the P/Ti molar ratio of 1 : 1.

Derivatization of diamondoids for functional applications

Diamondoids, a group of hydrocarbon cage molecules that resemble diamond lattice, are attracting increasing interest in the past decade. Their diamond-like structure warrants that diamondoids inherit the superior properties of diamond at nanoscale, including exceptional hardness and stiffness, high thermal stability, high chemical resistance, unique optical properties and fluorescence, and excellent biocompatibility. To effectively take advantage of the fascinating properties of diamondoids, they must be properly functionalized so that they can be covalently incorporated into the host systems or compatibly mixed with the hosts. Herein, the origin, synthesis, derivatization, and application of diamondoids are reviewed. In particular, how the derivatized diamondoids for various functional applications, including pharmaceuticals, polymers, fine chemicals, nanomaterials, and optical devices, are discussed. It is hoped that this review article can attract more interest in diamondoids, which in turn helps motivate the development of new synthesis and application of diamondoids and their derivatives so that this group of unique molecules can bring more benefits.

Electrochemical synthesis of dimethyl carbonate from CO2 and methanol over carbonaceous material supported DBU in a capacitor-like cell reactor

Electro-assisted dimethyl carbonate (DMC) formation from CO2 and methanol over carbonaceous material supported 1,8-diazabicyclo-[5.4.0]undec-7-ene (DBU) was first performed under solvent-free conditions in a capacitor-like cell reactor designed by our group. The effects of applied voltage modes and conductivities of the catalysts on the catalytic performances were fully investigated. The experiment results demonstrated that the catalytic activities can be obviously boosted when the voltages were applied to the catalyst fixed-bed. The constant working potential presented better catalytic activity than the metabolic voltages, and the higher conductivity of catalysts leads to a better catalytic performance. Furthermore, the supported DBU displayed good recyclable properties in the specially designed electrochemical apparatus. We proposed a reaction mechanism of the electrocatalysis for DMC formation.

New insight on facet-dependent physicochemical properties of anatase TiO2 nanostructures for efficient photocatalysis

Anatase TiO2, whose performance depends strongly on the exposed facets, is an efficient photocatalyst in utilizing solar energy for environmental purification. Herein, we report the synthesis of a series of TiO2 nanoparticles, with the {001} facet percentage adjusted in the range of ca. 0–100%. Comprehensive studies on the crystal structure evolution mechanisms and the corresponding influence on the physicochemical properties were conducted. Unlike previous results, we found that directly comparing the band gaps of TiO2 with different percentages of the {001} facet and the corresponding influence on the photocatalytic activity are infeasible. Experimental results indicate that 73% is the optimized {001} facet percentage for the most efficient photocatalysis. In addition to the traditional factors (e.g. crystallinity, specific surface area), this structure is also very efficient at separating the photo-carriers and adsorbing surface OH groups, which is different from previous results wherein more surface adsorbed F− ions result in less surface OH groups. This study may provide new insight on investigating the crystal facet engineering technique for efficient photocatalysis.

Innovative one-step synthesis of hollow polymer particles by microsuspension polymerization of styrene and methyl acrylate with Mg(OH) 2 as dispersant

Several methods consisting of two or multi-step processes have been so far proposed for the preparation of sub- and micrometer-sized hollow polymer particles. In this study, we proposed an innovative one-step synthesis of the hollow polymer particles by applying microsuspension copolymerization of styrene and methyl acrylate with Mg(OH)2 as dispersant. In this method, Mg(OH)2 acted not only as dispersant, which covered densely at the surface of the monomer droplets, but also caused hydrolysis reaction of MA unit within styrene-methyl acrylate copolymer particles during the polymerization due to giving alkaline pH in the aqueous medium. It is also important that methyl acrylates are predominantly polymerized over styrene at the initial stage of the microsuspension copolymerization.