Pollutants in wastewater, such as Cr(VI) is a continuous threat to our ecological system and human well-being because of its high noxiousness and latent carcinogenicity. Photocatalytic Cr(VI) reduction is the most suitable and eco-friendly way to convert the toxic Cr(VI) to environmentally friendly Cr(III). Porous metal−organic frameworks (MOFs) based nanocomposites are emerging green photocatalysts for Cr(VI) reduction due to their unique characteristics such as high photoconductivity, large surface area, and suitable porous structure. Herein, the preparation of ultrathin BiOCl sheets over UiO-66-NH 2 is reported for the first time at room temperature via a simplistic in situ synthetic process to yield a series of UiO-66-NH 2 @BiOCl-UTN's heterogeneous nano composites. The activity toward Cr(VI) reduction was tested under visible-light. UiO-66-NH 2 @BiOCl-UTN's heterogeneous nanocomposites exhibited better performance as equated to individual BiOCl and UiO-66-NH 2 , particularly the composite with Bi 3+ mole ratio of 5 mM surpassed other composites for photocatalytic Cr(VI) reduction. Furthermore, boosted visible-light absorption (λ > 420 nm) was observed in the presence of −NH 2 moiety on the organic linker. The excellent photocatalytic activity was attributed to the synergistic effect between BiOCl and UiO-66-NH 2 for the effective separation of photogenerated electron−hole suppressing their recombination. Through active species trapping experiments, electron spin resonance measurements, and electrochemical analysis, the reliable mechanism was predicted and confirmed. Moreover, heterogeneous nanomaterial retained its structure and activity for four consecutive cycles demonstrating its superior stability.
Selectively exposing active surfaces of Pt-based nanoframes (NFs) can promote electrocatalysis of small organic molecules, especially regarding improved diffusion and anti-poisoning properties. However, the systematic investigation on the synthesis, as well as structure-property relationship, of Pt-based NFs with tunable external and internal surface structures is still at its early stage. Herein, we report a facile, environmental and one-pot approach to fabricate PtCuNi NFs with tunable external and internal surface structures by flexibly adjusting coordination and reducing agents. Interestingly, electrocatalytic results reveal that the PtCuNi NFs with variable external structures possess higher performance (activity and anti-CO-poisoning capability) than those with tunable internal structures as well as commercial Pt/C. Especially, the PtCuNi eb-NFs (external branch NFs) exhibit the excellent specific activities of methanol and formic acid electrooxidation reactions (MOR and FAOR), 10.7 and 7.9 times higher than those of commercial Pt/C, respectively. The PtCuNi eb-NFs also possess a superior diffusion ability for methanol electrooxidation (0.0276) and formic acid electrooxidation (0.0153) compared to other PtCuNi NFs with plentiful internal surface. The enhanced MOR and FAOR activities of PtCuNi eb-NFs are ascribed to its abundant external surface area and high defect-density (e.g. vacancy, subtle lattice distortion and high-index facets), which results in an optimal anti-CO-poisoning capability due to the diffusion and ligand effects. This work opens up a new pathway for enhancing the electrooxidation properties (anti-poisoning property and diffusion rate) of liquid fuels by tuning the surface structures of nanoframe catalysts.
Heterogeneously catalyzed, selective hydrogenation in the liquid phase is widely used in industry for the synthesis of chemicals. However, it can be a challenge to prevent active nanoparticles (e.g., palladium) from aggregation/leaching and meanwhile achieve high conversion as well as selectivity, especially under mild conditions. To address these issues, a CeO2 nanotube/Pd@MIL‐53(Al) sandwich‐structured catalyst has been prepared in which the MIL‐53(Al) porous shell can efficiently stabilize the palladium nanoparticles. When this catalyst was used in a tandem catalytic reaction involving the dehydrogenation of ammonia borane and the hydrogenation of phenylacetylene, remarkably, the hydrogen released from the dehydrogenation of ammonia borane boosted the catalytic process, with 100 % conversion of phenylacetylene and a selectivity of 96.2 % for styrene, even at room temperature and atmospheric pressure, within 1 min. This work therefore provides an alternative strategy for balancing the conversion and selectivity of liquid‐phase hydrogenation reactions.
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