Generating and optimizing the catalytic activity in UiO-66 for aerobic oxidation of alkenes by post-synthetic exchange Ti atoms combined with ligand substitution

Photo- and Electrocatalytic Reduction of CO2 over Metal-Organic Frameworks and Their Derived Oxides: A Correlation of the Reaction Mechanism with the Electronic Structure

A Ce/Ti-based bimetallic 2-aminoterephthalate metal-organic framework (MOF) was synthesized and evaluated for photocatalytic reduction of CO₂ in comparison with an isoreticular pristine monometallic Ce-terephthalate MOF. Owing to highly selective CO₂ adsorption capability, optimized band gaps, higher flux of photogenerated electron-hole pairs, and a lower rate of recombination, this material exhibited better photocatalytic reduction of CO₂ and lower hydrogen evolution compared to Ce-terephthalate. Thorough probing of the surface and electronic structure inferred that the reducibility of Ce⁴⁺ to Ce³⁺ was due to the introduction of an amine functional group into the linker, and low-lying Ti(3d) orbitals in Ce/Ti-2-aminoterephthalate facilitated the photoreduction reaction. Both the MOFs were calcined to their respective oxides of Ce_1-xTi_xO₂ and CeO₂, and the electrocatalytic reduction of CO₂ was performed over the oxidic materials. In contrast to the photocatalytic reaction mechanism, the lattice substitution of Ti in the CeO₂ fluorite cubic structure showed a better hydrogen evolution reaction and consequently, poorer electroreduction of CO₂ compared to pristine CeO₂. Density functional theory calculations of the competitive hydrogen evolution reaction on the MOF and the oxide surfaces corroborated the experimental findings.

Modular Assembly of Electron Transfer Pathway in Bimetallic MOF for Photocatalytic Ammonia Synthesis

It is a long-term pursuit to implement the green and sustainable photocatalytic production of ammonia via the conversion of water and nitrogen under mild conditions. Due to the rapid recombination...

Advanced applications of Zr-based MOFs in the removal of water pollutants

The global water pollution is caused by the increase of industrial and agricultural activities, which have produced various toxic pollutants. Pollutants in water generally consist of metal ions, pharmaceuticals and personal care products (PPCPs), oil spills, organic dyes, and other organic pollutants. Amongst the adsorbents that have been developed to deal with pollutants in water, Zr-based metal-organic frameworks (MOFs) have drawn scientists' great attention due to their excellent stability and adjustable functionalization. Herein, the present review article introduces the synthetic methods of functionalized Zr-based MOFs and summarizes their applications in water pollution treatment. It also clarifies the interactions and removal mechanisms between pollutants and Zr-based MOFs. The use of these MOFs with eminent adsorption ability and recycling performance have been discussed in detail. Zr-based MOFs also face some challenges such as high cost, lack of real water environment applications, selective removal of pollutants, and low ability to remove composite pollutants. Future research should focus on addressing these issues. Although there is still a blank of the practical utility of Zr-based MOFs on a commercial scale, the research reported to date clearly shows that they are very promising materials for the water treatment.

Bifunctional metal–organic frameworks for the hydrogenation of nitrophenol using methanol as the hydrogen source

This work reports the reduction of 4-nitrophenol to 4-aminophenol using UiO-66(Zr) as a bifunctional photocatalyst and hydrogenation catalyst using methanol as the hydrogen source.

Promotional effect of Mn-doping on the catalytic performance of NiO sheets for the selective oxidation of styrene

The direct oxidation of styrene into high-value chemicals under mild reaction conditions remains a great challenge in both academia and industry. Herein, we report a successful electronic structure modulation of intrinsic NiO sheets via Mn-doping towards the oxidation of styrene. By doping NiO with only a small content of Mn (Mn/Ni atomic ratio of 0.030), a 75.0% yield of STO can be achieved under the optimized reaction conditions, which is 2.13 times higher than that of the pure NiO. In addition, the catalyst exhibits robust stability and good recycling performance. The performance enhancement originates from the synergistic effect regarding the abundant Ni(II) species, the rich oxygen vacancy sites and the large amount of surface redox centers. This work provides new findings of the elemental-doping-induced multifunctionality in designing powerful catalysts for the efficient and selective oxidation of styrene and beyond.

Hierarchical hollow nickel silicate microflowers for selective oxidation of styrene

Developing heterogeneous non-precious metal catalysts that can achieve high catalytic activity and good product selectivity at the same time is still a challenging and interesting work for the selective oxidation of styrene into valuable chemicals from environmental and industrial points of view. Herein, hierarchical hollow nickel silicate (Ni₃Si₂O₅(OH)₄) microflowers assembled from well-defined Ni₃Si₂O₅(OH)₄ nanosheets have been prepared by a facile one-pot hydrothermal method. The intriguing structure endows the hollow Ni₃Si₂O₅(OH)₄ microflowers a high surface area of 177.4 m² g^-1 and an average pore size of 3.9 nm. When employed as a catalyst for the selective oxidation of styrene in the presence of hydrogen peroxide as a ecological sustainable green oxidant, the Ni₃Si₂O₅(OH)₄ exhibits an attractive catalytic performance with a remarkably high styrene conversion of 99.3% and a high selectivity of 81.1% to benzaldehyde.

Ti functionalized hierarchical-pore UiO-66(Zr/Ti) catalyst for the transesterification of phenyl acetate and dimethyl carbonate

Uniformly distributed tetra-coordinated Ti^IV active sites grafted on hierarchical-pore UiO-66(Zr/Ti) as an efficient catalyst for synthesizing diphenyl carbonate.