Yongjuan Chen

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.

Reversible luminescence switch in a photochromic metal-organic framework.

Eu(III) ions have been introduced into a photoactive viologen system to yield a polyrotaxane-like metal-organic framework, which exhibits reversible photochromism and luminescence modulation with a non-destructive readout capability in the solid state.

Solvent- and anion-controlled photochromism of viologen-based metal–organic hybrid materials

Research on the tunable photosensitive properties of soft metal organic hybrid materials via environmental stimulation is presented. A supramolecular coordination polymer accommodating guest water molecules and anions is synthesized in aqueous solution. The original photochemically inert framework exhibits thermochromism, and can be transferred into a photochromic state via dehydration treatment. Furthermore, the interlayer ClO4− ions can be exchanged by halide and pseudohalide anions in a crystal to crystal manner. Although the favorable geometry for electron transfer from the carboxylate group to the bipyridinium moiety is created in transformed structures, the introduction of halide or pseudohalide anions leads to the formation of different charge transfer interactions with electron-accepting bipyridinium units in the ground state, which improves the light absorption of the compounds in the visible region and greatly affects the photoreduction efficiency of the bipyridinium unit. Consequently, the transformed crystals exhibit multicolor photochromic properties in solid states.

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.

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.