Mesoporous framework materials comprising lacunary [SiW11O39](8-) polyoxometalate clusters covalently connected by ethane-bridged silsesquioxane linkers were synthesized through a block copolymer-templated cross-linking polymerization of 1,2-bis(triethoxysilyl)ethane in acid solution. These new hybrid materials, which exhibit a high density of catalytic sites, large pore surface and ordered pore structure, are shown to be highly effective in the photocatalytic oxidation of aryl alcohols with molecular oxygen.
Increasing global environmental pollution
due to heavy metal ions
raises the importance of research on new multifunctional materials
for simultaneous detection and removal of these contaminants from
water resources. In this study, we report a microporous 8-connected
Zr4+ metal–organic framework (MOF) based on a terephthalate
ligand decorated with a chelating 2-picolylamine side group (dMOR-2), which shows highly efficient fluorescence sensing
and sorption of heavy metal cations. We demonstrate by detailed fluorescence
studies the ability of a water-dispersible composite of dMOR-2 with polyvinylpyrrolidone for real-time detection of Cu2+, Pb2+, and Hg2+ in aqueous media. The limits
of detection were found to be below 2 ppb for these species, while
the system’s performance is not affected by the presence of
other potentially competitive ions. In addition, sorption studies
showed that a composite of dMOR-2 with calcium alginate
(dMOR-2@CaA) is an excellent sorbent for Pb2+ and Cu2+ ions with capacities of 376 ± 15 and 117
± 4 mg per gram of dMOR-2@CaA, respectively, while
displaying the capability for simultaneous removal of various heavy
metal ions in low initial concentrations and in the presence of large
excesses of other cationic species. Structural and spectroscopic studies
with model ligands analogous to our material’s receptor unit
showed chelation to the 2-picolylamine moiety to be the main binding
mode of metal ions to dMOR-2. Overall, dMOR-2 is shown to represent a rare example of a MOF, which combines sensitive
fluorescence detection and high sorption capacity for heavy metal
ions.
Understanding of photochemical charge transfer processes at nanoscale heterojunctions is essential in developing effective catalysts. Here, we utilize a controllable synthesis method and a combination of optical absorption, photoluminescence, and electrochemical impedance spectroscopic studies to investigate the effect of MoS2 nanosheet lateral dimension and edge length size on the photochemical behavior of MoS2‐modified graphitic carbon nitride (g‐C3N4) heterojunctions. These nano‐heterostructures, which comprise interlayer junctions with variable area (i. e., MoS2 lateral size ranges from 18 nm to 52 nm), provide a size‐tunable interfacial charge transfer through the MoS2/g‐C3N4 contacts, while exposing a large fraction of surface MoS2 edge sites available for the hydrogen evolution reaction. Importantly, modification of g‐C3N4 with MoS2 layers of 39±5 nm lateral size (20 wt % loading) creates interfacial contacts with relatively large number of MoS2 edge sites and efficient electronic transport phenomena, yielding a high photocatalytic H2‐production activity of 1497 μmol h−1 gcat−1 and an apparent QY of 3.3 % at 410 nm light irradiation. This study thus offers a design strategy to improve light energy conversion efficiency of catalysts by engineering interfaces at the nanoscale in 2D‐layered heterojunction materials.
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