Xinxin Xu

Hybrid material based on a coordination-complex-modified polyoxometalate nanorod (CC/POMNR) and PPy: a new visible light activated and highly efficient photocatalyst

To improve the photocatalytic activity of a coordination-complex-modified polyoxometalate (CC/POM), a new type of hybrid material (abbreviated as PPy/CC/POMNR) was fabricated by the combination of its nanorod (CC/POMNR) and polypyrrole (PPy) via a facile in situ chemical oxidation polymerization process under the initiation of ammonium persulfate (APS). Under the irradiation of visible light, PPy/CC/POMNR exhibited higher photocatalytic activity compared to CC/POMNR, PPy, and their mechanically blended products formed on the degradation of Rhodamine B (RhB). Optical and electrochemical tests showed that the enhancement of photocatalytic performance can be attributed to the high separation efficiency of the photogenerated electrons and holes on the interface of CC/POMNBs and PPy, which results from the synergistic effect between them. Furthermore, the influence of the concentration ratio between pyrrole (Py) and APS on the morphology, conductivity, and photocatalytic properties of the PPy/CC/POMNR is discussed and the optimal condition to fabricate a hybrid material with high efficiency was determined. These results suggest that the hybrid of CC/POMNR and PPy would be a feasible strategy to enhance the photocatalytic activity of CC/POMNR.

Photocatalytic activity of transition-metal-ion-doped coordination polymer (CP): photoresponse region extension and quantum yields enhancement via doping of transition metal ions into the framework of CPs

To improve photocatalytic activity of a coordination polymer (CP) in the visible light region, five different transition metal ions (Fe(3+), Cr(3+), Ru(3+), Co(2+) and Ni(2+)) were introduced into its framework through an ion-exchange process. Among all the resulting transition metal ion doped coordination polymers (TMI/CPs), the one doped with Fe(3+) took on the most excellent photocatalytic activity and the highest quantum yields in the visible light region, decomposing 94% Rhodamine B (RhB) in 8 hours. It can be attributed to the doping of Fe(3+), which reduced the band gap (Eg) of the original CP, facilitating photocatalysis of the obtained polymer. Compared with the coordination polymer with Fe(3+) as a dopant, products doped with other metal ions presented weaker photocatalytic activities in the visible light region, while under the irradiation of ultraviolet light, they showed favorable photocatalytic properties. The results suggest that to dope transition metal ions into the framework of CPs would be an ideal option for enhancing the photocatalytic activity of coordination polymers.

Effect of the site of hydrogen-bonding on the liquid crystalline behaviour of supramolecular complexes

Two series of hydrogen-bonded side-chain liquid crystal polymers have been prepared by mixing components containing carboxyl acid and pyridyl-based fragments. We have focused our attention on the effect that the position of the hydrogen bond donor or acceptor site attached to the side-chain backbone has on the hydrogen-bonding interactions and liquid crystalline phase transitions of the system. The liquid crystalline behaviour of the complexes is studied using Fourier transform infrared spectroscopy, differential scanning calorimetry, polarising optical microscopy and X-ray diffraction. The results indicate that the phase transition temperatures of the complexes are influenced by the site of hydrogen-bonding.

Chemical‐Bond‐Mediated p–n Heterojunction Photocatalyst Constructed from Coordination Polymer Nanoparticles and a Conducting Copolymer: Visible‐Light Active and Highly Efficient

A visible-light-active p-n heterojunction photocatalyst has been synthesized by the enwrapping of poly[aniline-co-N-(4-sulfophenyl)aniline] (PAPSA) on a coordination polymer nanoparticle (NCP). Compared with the visible-light-inactive NCP, the new p-n heterojunction photocatalyst, PAPSA/NCP, exhibits a much higher efficiency in the reduction of Cr(VI) under visible light. PAPSA performs two functions in this p-n heterojunction photocatalyst. First, as a visible-light-active material, it extends the photoresponse region of the photocatalyst from the ultraviolet to the visible-light region. Secondly, as a p-type semiconductor possessing suitable energy levels with respect to NCP, PAPSA forms a p-n heterojunction with the n-type NCP; the inner electric field of the p-n heterojunction accelerates the separation of electrons and holes, which enhances the photocatalytic efficiency. Furthermore, the p-n heterojunction photocatalyst exhibits outstanding stability during the photocatalytic reduction of Cr(VI) .

The fabrication of a nanoscale polyoxometalate based magnetic adsorbent and its selective adsorption on cationic dyes

Abstract Amino group-functionalized Fe3O4 is loaded on a coordination complex-modified polyoxometalate nanoparticle. In this composite material, Fe3O4 and coordination complex-modified polyoxometalate are connected with intense hydrogen bonds as suggested by FTIR. This composite material exhibits excellent methylene blue (MB) adsorption, with adsorption capacity of 175.5 mg g−1. It also possesses selective separation ability between cationic and anionic dye molecules. In binary solution of MB and methyl orange (MO), MB adsorption efficiency reaches 75%, but it exhibits almost no effect on the adsorption of methyl orange. The saturation magnetization value of this composite material is 18.89 emu g−1, allowing magnetic separation, which facilitates the recycle and reuse of this composite adsorbent.

Coordination polymer derived Ni based composite material with N-doped mesoporous carbon as matrix for pollutants removal

To obtain a magnetic composite material for water treatment, a Ni based composite material with nitrogen doped mesoporous carbon as matrix (Ni@NC) has been synthesized with coordination polymer as precursor. In Ni@NC, Ni nanoparticle with the size about 3–5xa0nm dispersed evenly in nitrogen doped mesoporous carbon matrix. Ni@NC exhibits striking catalytic activity in reductive conversion of 4-nitrophenol to 4-aminophenol with the existence of sodium borohydride (NaBH4). The conversion efficiency reaches almost 100% in 160xa0s with the amount of Ni@NC as low as 5xa0mg. After eight successive cycles of reductions, the efficiency still retains above 99%. For a catalyst, chemical content plays an important role in its performance. Here, the influence of nitrogen species on 4-nitrophenol reductive property is discussed in detail, which illustrates pyrrolic N and quaternary N both play significant roles during catalytic reduction process. In addition, Ni@NC also possesses excellent activity in catalytic reduction of organic dyes, such as Rhodamine B (RhB), methyl orange (MO) and methylene blue (MB). Due to its large surface area and suitable pore size, Ni@NC also possesses adsorption removal property towards tetracycline and Cr2O72−. Magnetic measurement reveals ferromagnetic character of Ni@NC, which facilitates its magnetic separation from the treated samples. All these merits make Ni@NC a promising multifunctional environmental material in waste water treatment.

The loading of polyoxometalates compound on a biomass derived N-doped mesoporous carbon matrix, a composite material for electrical energy storage

Abstract A polyoxometalate (POM)-based composite material (NiPW12NP/NMC) was synthesized, in which the nanoparticle of a POM compound (NiPW12NP) distributes on orange juice derived nitrogen doped mesoporous carbon matrix (NMC) homogenously. When employed as a cathode material, NiPW12NP/NMC exhibits high specific capacitance, remarkable rate capability and long-term stability. When the current density is 4u2009A·g−1, a specific capacitance as high as 547 F·g−1 is achieved by NiPW12NP/NMC. With NiPW12NP/NMC serving as cathode and MnO2 acting as anode, a high performance asymmetric supercapacitor is assembled, which possesses a high energy density of 10.88u2009Wh·kg−1 at 0.64u2009kW·kg−1. It also shows a good rate capability, when the current density increases from 4 to 12u2009A·g−1, its specific capacitance decreases from 113 to 88 F·g−1, with 77.9% capacitance retention. After 5000 cycles charge-discharge experiments, 92.8% of its capacitance can be maintained, which exhibits good stability.

Three-dimensional supramolecular phosphomolybdate architecture-derived Mo-based electrocatalytic system for overall water splitting

With hydrogen bond-directed three-dimensional phosphomolybdate-based supramolecular architecture as a precursor, a Mo2C composite material (Mo2C@NC) supported by nitrogen-doped carbon matrix was fabricated successfully through calcination. In this composite material, Mo2C particles with size about 5 to 8 nm disperse evenly in the framework of nitrogen-doped mesoporous carbon matrix. In acid media, to achieve a current density of 10 mA cm−2, the overpotential required was 142 mV with a Tafel slope of 63 mV dec−1. Under basic conditions, the overpotential reduced to as low as 56 mV with a Tafel slope of 59 mV dec−1. To realize overall water splitting, MoO2-based composite material (MoO2@NC) with nitrogen-doped carbon as matrix was obtained using the same precursor as Mo2C@NC. MoO2@NC exhibits excellent oxygen evolution reaction (OER) performance with an over potential of 302 mV. With Mo2C@NC as cathode and MoO2@NC as anode, an efficient electrolyzer was constructed, which required a cell voltage of 1.60 V to achieve a current of 10 mA cm−2 in 1.0 M KOH. Furthermore, besides overall water splitting, Mo2C@NC also shows striking catalytic removal property towards 4-nitrophenol and Rhodamine B.

Sulfur vacancy-rich CdS loaded on filter paper-derived 3D nitrogen-doped mesoporous carbon carrier for photocatalytic VOC removal

A simple method is developed for the synthesis of a sulfur vacancy-rich CdS-based composite photocatalyst with a three-dimensional nitrogen-doped mesoporous carbon matrix using a Cd(II)-based coordination polymer and filter paper as precursors. Using this strategy, an excellent composite photocatalyst (CdS@3D-NPC) is synthesized successfully, in which CdS nanoparticles with a small size (about 6 to 8 nm) are distributed homogenously in the three-dimensional nitrogen-doped mesoporous carbon matrix. During calcination, some coordinated nitrogen atoms from the organic ligands occupy the sites of S2− and dope in the lattice of CdS, which produces abundant sulfur vacancies. These sulfur vacancies promote the transportation of photogenerated electrons and their separation from photogenerated holes, which enhance the photocatalytic activity of the composite material. CdS@3D-NPC shows a promising performance for the decomposition of volatile organic compounds (VOCs), such as formaldehyde and benzene gas. The stability and durability of CdS@3D-NPC are outstanding. Its VOC removal efficiency remains as high as 95% of the original value after five continuous cycles of photocatalytic reaction for 30 h. The mechanism study illustrates that the excellent VOC removal performance originates from the synergetic effect of sulfur vacancies and excellent conductivity of the three-dimensional nitrogen-doped mesoporous carbon matrix. We anticipate that CdS@3D-NPC will be employed as an ideal tool for indoor air purification.

A carbon based drug delivery system derived from a one-dimensional coordination polymer, doxorubicin loading and redox-responsive release

Since the controlled release of drug molecules under external stimuli is an essential strategy for effective tumor therapy, herein a redox-responsive drug delivery system (Ag-SS-MC) has been fabricated successfully through the modification of disulfide bonds on coordination polymer derived mesoporous carbon nanoparticles (MC) with nanoscale Ag as the “cap”. In this drug delivery system, the Ag “caps” are fastened on a disulfide linker tightly, which blocks the pores of MC and impedes unexpected leakage of loaded doxorubicin (DOX). This drug delivery system exhibits a striking DOX loading property, with loading ratio as high as 20.6%. Ag-SS-MC remains stable under normal physiological conditions, but the loaded DOX begins to be released in the presence of a reducing agent, glutathione (GSH), which is caused by reductive breaking of disulfide bonds. MTT assays show that, after incubation with the human cervical cancer cell line (HeLa) for 24 h, the cytotoxicity of blank Ag-SS-MC carriers can almost be ignored. In contrast, under the same conditions, the DOX loaded drug carrier system possesses high antitumor activity. Ag-SS-MC exhibits superior drug loading, high extracellular stability, redox-responsive intracellular drug release and excellent biocompatibility; all these characteristics make it a promising drug delivery system for tumor therapy.