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The particle size of co-catalysts significantly affects the activity of semiconductors in photocatalysis. Herein, we report that the photocatalytic H 2 evolution (PHE) activity of a visible light responsive covalent organic framework (COF) layer supported on SiO 2 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 g COF −1 h −1 and apparent quantum efficiency up to 7.3% were achieved with the Pd SAs/Cs cocatalyst. The relationship between the activity of Pd in H 2 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 H 2 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.

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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.

The three bipyridine-proline chiral ligands (Z) with different structural units as highly active species were successfully introduced on Zn-modified bimodal mesoporous silicas (BMMs). The representative heterogeneous catalysts (ZZnBMMs-n) containing different molar ratios of Z/Zn (5, 20, 50, 100, 200%) were prepared, and their catalytic performances were evaluated in the asymmetric aldol reactions between p-nitrobenzaldehyde and cyclohexanone, showing the satisfactory activities (yields) and good stereoselectivity (dr and ee). Meanwhile, their microstructural features and physicochemical properties were characterized by various methods. Particularly, the fractal evolution, the pair distance distribution function, and the Porod plots of the ZZnBMMs catalysts were demonstrated by SAXS analysis. The results revealed that the interfacial layer thickness and their mass fractal (D m ) value gradually increased with the enhanced molar ratios of Z/Zn, along with the decrease of pore size and densification of volume, suggesting the successful Z-grafting into the mesoporous channels of Zn-modified matrixes. The essential relationships between the fractal features and their catalytic performance (yield, dr and ee) were explored, showing the larger the D m values, the better catalytic performance. Besides, the uniform distributions of Zn and S elements in ZZnBMMs catalysts and the formation of enamine-imine intermediates during the asymmetric aldol reactions were confirmed.