Fabrication of Functionalized UiO-66 Anchored on Disorderly Layered Clinoptilolite via Surfactant-Assisted Induction for Selective Adsorption of CO2 and CH4.

The amine (NH2)-functionalized UiO-66 was successfully anchored on disorderly layered clinoptilolite (CP) via surfactant (poly(ethylene glycol) (PEG) and poly(vinylpyrrolidone) (PVP))-assisted induction. The structural features and physicochemical parameters of the resultant UiO-66-on-CPs were characterized by powder X-ray diffraction (XRD) patterns, scanning/transmission electron microscopy (SEM/TEM) images, Fourier transform infrared (FT-IR) spectra, N2 sorption isotherms, and small-angle X-ray scattering (SAXS) patterns. The results demonstrated that the growth of UiO-66-NH2 nanoparticles facilitated the disorder degree of the crystal plane of CP along the a-axis, while the addition of PEG in the hydrothermal synthesis system of CP was conducive to the formation of a flower-like microstructure and the introduction of PVP was beneficial to the nucleation and growth of UiO-66-NH2 nanoparticles with a small size (40 nm) on the surfaces of the obtained CP-PEG lamellas. Finally, the gas-selective adsorption and separation performances of CO2 and CH4 were evaluated using the synthesized disorderly layered UiO-66-on-CP heterostructures as adsorbents, indicating that the NH2-functionalized UiO-66-on-CP exhibited a superior selective factor (3.66) of CO2/CH4. These results elucidated that the proposed approach is a promising strategy for constructing MOF-on-zeolite heterostructures, which may open an avenue to expand CP application and improve their performance.

Comparison of mesoporous fractal characteristics of silica-supported organocatalysts derived from bipyridine-proline and resultant effects on the catalytic asymmetric aldol performances.

Three kinds of the bipyridine-proline chiral ligands as highly active species were successfully introduced on Zn-modified mesoporous silica nanomaterials (BMMs, MCM-41, and SBA-15) via the covalent attachment and coordination methods. Their microstructural features and physicochemical properties were extensively characterized via XRD patterns, SEM/TEM images, TGA profiles, FT-IR and UV-Vis spectra. In particular, their fractal features, the pair distance distribution function, and the Porod plots were evaluated thoroughly on the basis of the SAXS data. Meanwhile, their catalytic performances for asymmetric aldol reactions between p-nitrobenzaldehyde and cyclohexanone were evaluated. The results indicated that the bimodal mesoporous BMMs-based samples with short worm-like mesoporous channels possessed both mass and surface fractal features, whereas the MCM-41- and SBA-15-based samples with long-range ordered structures only showed surface fractal features. The influences of various reaction parameters, including the textures of the mesoporous silicas, the structures of the used chiral ligands, and the molecular volumes of aldehydes, on the catalytic activities (yield) and stereoselectivities (dr and ee) were investigated thoroughly. The results showed satisfactory activities (yields) and better stereoselectivity (dr and ee) in comparison with the homogeneous catalytic system using Z as the catalysts. In particular, the 3rd recycle catalytic performances of the Z-immobilized heterogeneous catalysts retained high catalytic yields (around 80%) and ee values of 28%. These phenomena were well interpreted by the essential relationships between the fractal characteristics of these heterogeneous catalysts and their catalytic activities.

The Fabrication of Pd Single Atoms/Clusters on COF Layers as Co-catalysts for Photocatalytic H2 Evolution.

The particle size of co-catalysts significantly affects the activity of semiconductors in photocatalysis. Herein, we report that the photocatalytic H2 evolution (PHE) activity of a visible light responsive covalent organic framework (COF) layer supported on SiO2 nanoparticles was greatly promoted from 47.7 to 85.5 µmol/h by decreasing the particle size of the Pd co-catalyst from 3.3 nm to single atoms/clusters. A PHE rate of 156 mmol gCOF-1 h-1 and apparent quantum efficiency up to 7.3% were achieved with the Pd SAs/Cs co-catalyst. The relationship between the activity of Pd in H2 dissociation, proton reduction, and PHE rate suggests that the promotion effect of Pd SAs/Cs is mainly attributed to their enhancement in charge separation of COF layers rather than proton reduction. Furthermore, a photoactive film was fabricated and steady production of H2 was achieved under visible light irradiation and static conditions. The optimization of the particle size of co-catalysts provides an efficient method for enhancing the photocatalytic activity of semiconductors.