Zhiying Yan

A dye-sensitized Pt@UiO-66(Zr) metal–organic framework for visible-light photocatalytic hydrogen production

A stable photoactive metal-organic framework UiO-66(Zr) sensitized by adsorbed or directly added rhodamine B dye exhibited photocatalytic activity for hydrogen evolution under visible-light illumination (λ≥ 420 nm). Using Pt as a co-catalyst, the adsorbed and directly added dye extremely enhanced the photocatalytic activity to 30 and 26 times the value afforded by bare Pt@UiO-66(Zr), respectively.

UV and solar light degradation of dyes over mesoporous crystalline titanium dioxides prepared by using commercial synthetic dyes as templates

Although photosensitization of titania by organic dyes is one of the conventional ways for visible-light utilization of titania, previous studies have not yet addressed the use of dyes as templates in the synthesis of mesoporous materials, let alone the simultaneous achievement of highly crystalline mesoscopic ordering and visible-light photocatalytic activity. In this work, fourteen commercial synthetic dyes were directly used as structure-directing agents which convert to carbonaceous materials after 400 °C calcination in synthesis of thermally stable mesostructured titania. This in situ carbon enhanced the visible light photocatalytic activities for the degradation of aqueous dyes. The synthesized mesoporous titania samples were characterized by a combination of various physicochemical techniques, such as XRD, SEM, HRTEM, nitrogen adsorption/desorption, TGA–DSC, XPS, diffuse reflectance UV–vis and FT–IR. Most of prepared mesoporous titania photocatalysts exhibited better activity under outside solar light than under artificial UV light, due to the presence of carbonaceous species which were transferred from the dye templates. The reported strategies combine sol-gel chemistry and self-assembly routes directly using dye templates that tune the materials architecture, texture and particularly function, visible-light photocatalysis.

MOFzyme: Intrinsic protease-like activity of Cu-MOF

The construction of efficient enzyme mimetics for the hydrolysis of peptide bonds in proteins is challenging due to the high stability of peptide bonds and the importance of proteases in biology and industry. Metal-organic frameworks (MOFs) consisting of infinite crystalline lattices with metal clusters and organic linkers may provide opportunities for protease mimic which has remained unknown. Herein, we report that Cu2(C9H3O6)4/3 MOF (which is well known as HKUST-1 and denoted as Cu-MOF here), possesses an intrinsic enzyme mimicking activity similar to that found in natural trypsin to bovine serum albumin (BSA) and casein. The Michaelis constant (Km) of Cu-MOF is about 26,000-fold smaller than that of free trypsin indicating a much higher affinity of BSA for Cu-MOF surface. Cu-MOF also exhibited significantly higher catalytic efficiency than homogeneous artificial metalloprotease Cu(II) complexes and could be reused for ten times without losing in its activity. Moreover, Cu-MOF was successfully used to simulate trypsinization in cell culture since it dissociated cells in culture even without EDTA.

Catalytic hydrothermal conversion of carboxymethyl cellulose to value-added chemicals over metal–organic framework MIL-53(Al)

Catalytic hydrolysis of biomass over solid catalysts can be one of the most efficient pathways for a future sustainable society dependent on cellulose biomass. In this work metal-organic framework MIL-53(Al) without any functionalization was directly employed as an efficient heterogeneous catalyst for the hydrolysis of carboxymethyl cellulose (CMC) to 5-hydroxymethyl-furaldehyde (5-HMF) in aqueous phase. A 5-HMF molar yield of 40.3% and total reducing sugar (TRS) molar yield of 54.2% were obtained with water as single solvent at 473 K for 4 h. The catalyst could be reused three times without losing activity to a greater extent. With the remarkable advantages such as the use of water as single solvent and MIL-53(Al) as a novel heterogeneous green catalyst, the work provides a new platform for the production of value added chemicals and liquid fuels from biomass.

PVP-Capped Silver Nanoparticles as Catalyst for Oxidative Coupling of Thiols to Disulfides

Abstract Polyvinylpyrrolidone (PVP)-capped silver nanoparticles were used as the catalyst for the oxidative coupling of n -dodecanethiol. The product was characterized to be n -dodecyl disulfide by mass spectrometry, Fourier transform infrared spectroscopy, Raman spectros-copy, and proton nuclear magnetic resonance spectroscopy. The effects of reaction time, temperature, catalyst concentration, and water amount on catalyst performance were examined. The optimum reaction conditions were 0.157 mmol PVP-capped silver nanoparticles, 20 μl distilled water, reaction temperature of 100 °C, and reaction time of 3 h. The PVP-capped silver nanoparticles were also used as the catalyst for the oxidative coupling of n -butanethiol and n -octanethiol to their corresponding disulfides.

Synthesis and photocatalysis of mesoporous titania templated by natural rubber latex

Although a few systems prepared by using biotemplates have been employed as mesoporous photocatalysts, the natural latex secreted by plants has not been used as a template to synthesize porous materials, let alone for the achievement of high photocatalytic activity under solar light. Herein, one of the most important biosynthesized polymers, natural rubber latex from the rubber tree, Hevea brasiliensis in Xishuangbanna was directly used as a structure-directing agent in synthesis of thermally stable mesostructured TiO2. The as-prepared samples were characterized by XRD, FT-IR, XPS, N2 adsorption/desorption, TEM and UV-vis DRS. The synthesized TiO2 exhibited highly effective photocatalytic activity for the degradation of phenol and rhodamine B under solar light. Furthermore, addition of acetylacetone (ACA) during the synthesis significantly enhanced the photocatalytic activity. The reported strategies provide a new direction of using natural rubber latex as a template to prepare highly effective photocatalysts.

Visible-Light Degradation of Dyes and Phenols over Mesoporous Titania Prepared by Using Anthocyanin from Red Radish as Template

Heterogeneous photocatalysis is able to operate effectively to eliminate organic compounds from wastewater in the presence of semiconductor photocatalyst and a light source. Although photosensitization of titania by organic dyes is one of the conventional ways for visible-light utilization of titania, previous studies have not yet addressed the use of natural food coloring agents as templates in the synthesis of mesostructured materials, let alone the simultaneous achievement of highly crystalline mesoscopic framework and visible-light photocatalytic activity. In this work, anthocyanin, a natural pigment from red radish was directly used as template in synthesis of highly crystalline mesoporous titania. The synthesized mesoporous titania samples were characterized by a combination of various physicochemical techniques, such as XRD, SEM, HRTEM, nitrogen adsorption/desorption, and diffuse reflectance UV-Vis. The prepared mesoporous titania photocatalyst exhibited significant activity under visible-light irradiation for the degradation of dyes and phenols due to its red shift of band-gap-absorption onset and visible-light response as a result of the incorporation of surface carbon species.

Biogenic C-doped titania templated by cyanobacteria for visible-light photocatalytic degradation of Rhodamine B.

Cyanobacteria, which occurred in eutrophic water harvest solar light to carry out photosynthesis with high efficiency. In this work, cyanobacteria (Microcystis sp.) were used as biotemplate to synthesize titania structure. The synthesized titania sample had similar morphology to that of the original template in spite of the fragile unicellular structures and extremely high water content of cyanobacterial cells. Incorporation of biogenic C, as well as the morphology inherited from biotemplate improved visible-light absorbance of the titania structure. The sample exhibited higher visible-light photocatalytic activity than commercial titania photocatalyst Degussa P25 for Rhodamine B (RhB) degradation. Compared with those C-doped titania photocatalysts prepared by other methods, cyanobacteria templated titania photocatalyst offer some potential for competitive advantages. The reported strategy opened up a new use for the cyanobacteria. It could also be used for titania in applications such as treatment of polluted water, dye-sensitized solar cells, or other regions.

Visible light photodegradation of rhodamine B over VDF/CTFE copolymer-templated crystalline mesoporous titania

Mesoporous TiO2 with anatase crystalline structure (MTiO2/F2319) has been synthesized by using vinylidene fluoride/chlorotrifluoroethylene copolymer (1:9 in mole, F2319) as template. The synthesized mesoporous titania samples were characterized by a combination of various physicochemical techniques, such as X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, and N2 adsorption/desorption. It was found that without any external doping, MTiO2/F2319 exhibited significantly higher photocatalytic activities for the degradation of rhodamine B (RhB) dye than P25 TiO2 under visible light irradiation. Furthermore, the UV-Vis absorption maximum of the dye solution exhibited a gradual hypsochromic shift due to de-ethylation and degradation of RhB dye.