A new biomimetic heterogeneous photocatalyst ([FeFe]@ZrPF) has been synthesized through the incorporation of homogeneous complex 1 [(í-SCH2)2NC(O)C5H4N]-[Fe2(CO)6] into the highly robust zirconium-porphyrin based metal-organic framework (ZrPF). The immobilized biomimetic [Fe2S2] catalyst inside the MOF shows great improvement in hydrogen generation compared to the reference homogeneous catalyst complex 1.
High-silica zeolites, as exemplified by ZSM-5, with excellent chemical and thermal stability, have generated a revolution in industrial catalysis. In contrast, prior to this work, high-silica-zeolite-like chalcogenides based on germanium/tin remained unknown, even after decades of research. Here six crystalline high-germanium or high-tin zeolite-type sulfides and selenides with four different topologies are reported. Their unprecedented framework compositions give these materials much improved thermal and chemical stability with high surface area (Langmuir surface area of 782 m(2)/g(-1)) comparable to or better than zeolites. Among them, highly stable CPM-120-ZnGeS allows for ion exchange with diverse metal or complex cations, resulting in fine-tuning in porosity, fast ion conductivity, and photoelectric response. Being among the most porous crystalline chalcogenides, CPM-120-ZnGeS (exchanged with Cs(+) ions) also shows reversible adsorption with high capacity and affinity for CO2 (98 and 73 cm(3) g(-1) at 273 and 298 K, respectively, isosteric heat of adsorption = 40.05 kJ mol(-1)). Moreover, CPM-120-ZnGeS could also function as a robust photocatalyst for water reduction to generate H2. The overall activity of H2 production from water, in the presence of Na2S-Na2SO3 as a hole scavenger, was 200 μmol h(-1)/(0.10 g). Such catalytic activity remained undiminished under illumination by UV light for as long as measured (200 h), demonstrating excellent resistance to photocorrosion even under intense UV radiation.
We demonstrate an additive manufacturing approach to produce gradient refractive index glass optics. Using direct ink writing with an active inline micromixer, we three-dimensionally print multimaterial green bodies with compositional gradients, consisting primarily of silica nanoparticles and varying concentrations of titania as the index-modifying dopant. The green bodies are then consolidated into glass and polished, resulting in optics with tailored spatial profiles of the refractive index. We show that this approach can be used to achieve a variety of conventional and unconventional optical functions in a flat glass component with no surface curvature.
Self-doped TiO2 shows visible light photocatalytic activity, while commercial TiO2 (P25) is only UV responsive. The incorporation of Ti(3+) into TiO2 structures narrows the band gap (2.90 eV), leading to significantly increased photocatalytic activity for the reduction of CO2 into a renewable hydrocarbon fuel (CH4) in the presence of water vapour under visible light irradiation.
Direct
ink writing (DIW) three-dimensional (3D) printing provides
a revolutionary approach to fabricating components with gradients
in material properties. Herein, we report a method for generating
colloidal germania feedstock and germania–silica inks for the
production of optical quality germania–silica (GeO2–SiO2) glasses by DIW, making available a new material
composition for the development of multimaterial and functionally
graded optical quality glasses and ceramics by additive manufacturing.
Colloidal germania and silica particles are prepared by a base-catalyzed
sol–gel method and converted to printable shear-thinning suspensions
with desired viscoelastic properties for DIW. The volatile solvents
are then evaporated, and the green bodies are calcined and sintered
to produce transparent, crack-free glasses. Chemical and structural
evolution of GeO2–SiO2 glasses is confirmed
by nuclear magnetic resonance, X-ray diffraction, and Raman spectroscopy.
UV–vis transmission and optical homogeneity measurements reveal
comparable performance of the 3D printed GeO2–SiO2 glasses to glasses produced using conventional approaches
and improved performance over 3D printed TiO2–SiO2 inks. Moreover, because GeO2–SiO2 inks are compatible with DIW technology, they offer exciting options
for forming new materials with patterned compositions such as gradients
in the refractive index that cannot be achieved with conventional
manufacturing approaches.
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