Effect of linker and metal on photoreduction and cascade reactions of nitroaromatics by M-UiO-66 metal organic frameworks

High performance photocatalyst TiO2@UiO-66 applied to degradation of methyl orange

MOFs have considerable adsorption capacity due to their huge specific surface area. They have the characteristics of photocatalysts for their organic ligands can absorb photons and produce electrons. In this paper, the photodegradation properties of TiO2 composites loaded with UiO-66 were investigated for the first time for MO. A series of TiO2@UiO-66 composites with different contents of TiO2 were prepared by a solvothermal method. The photocatalytic degradation of methyl orange (MO) was performed using a high-pressure mercury lamp as the UV light source. The effects of TiO2 loading, catalyst dosage, pH value, and MO concentration were investigated. The results showed that the degradation of MO by TiO2@UiO-66 could reach 97.59% with the addition of only a small amount of TiO2 (5 wt%). TiO2@UiO-66 exhibited significantly enhanced photoelectron transfer capability and inhibited efficient electron-hole recombination compared to pure TiO2 in MO degradation. The composite catalyst indicated good stability and reusability when they were recycled three times, and the photocatalytic reaction efficiencies were 92.54%, 88.76%, and 86.90%. The results provide a new option to design stable, high-efficiency MOF-based photocatalysts.

Adenosine-functionalized UiO-66-NH2 to efficiently remove Pb(II) and Cr(VI) from aqueous solution: Thermodynamics, kinetics and isothermal adsorption

A new zirconium-based adsorption material (UiO-66-AMP) was prepared by modifying UiO-66-NH₂ with 5-adenosine to effectively remove Pb(II) and Cr(VI) from wastewater. The SEM, EDS, XRS and FT-IR characterization confirmed the successful synthesis of UiO-66-AMP. We conducted a sets of experiments to test the adsorption effectiveness of UiO-66-AMP for Pb(II) and Cr(VI). The maximum adsorption capacity of UiO-66-AMP for Cr(VI) (pH=2) and Pb(II) (pH=4) are 196.60 and 189.69 mg/g, respectively. The adsorption process conforms to the pseudo-second-order and Langmuir models, which indicates that the adsorption is a single-layer chemical process. Gibbs free energy (∆G) indicates that the adsorption of Pb(II) is an exothermic reaction, while the adsorption of Cr(VI) is an endothermic reaction. At the same time, the adsorbent maintains excellent adsorption capacity at least after 4 cycles. The good adsorption performance of UiO-66-AMP towards the metal ions was attributed to the surface complexation and electrostatic interactions. Therefore, the new adsorbent has obvious application prospect to remove Pb(II) and Cr(VI) from wastewater.

Facile preparation of ultrafine Pd nanoparticles anchored on covalent triazine frameworks catalysts for efficient N-alkylation

The fabrication of stable and efficient catalysts for green and economic catalytic transformation is significant. Here, highly stable covalent triazine frameworks (CTF-1) were used as the supporting material for anchoring ultrafine Pd nanoparticles (NPs) via a facile impregnation process and a one-pot calcination-reduction strategy. The widespread dispersion of ultrafine Pd NPs was a result of the abundant high nitrogen-content triazine groups of CTF-1 that endowed the catalyst Pd@CTF-1 with high catalytic activity. The catalytic performance of Pd@CTF-1 was demonstrated by the one-pot N-alkylation of benzaldehyde with aniline (or nitrobenzene) under mild reaction conditions, and Pd@CTF-1 exhibited a wide range of general applicability for N-alkylation reactions. The reaction mechanism for the N-alkylation reaction was also studied in detail. In addition, the Pd@CTF-1 catalyst exhibited high thermal and chemical stability, maintaining good catalytic efficiency after multiple reaction cycles. This study provides new insights for the fabrication of organic supporting materials with highly dispersed active catalytic sites that can lead to excellent catalytic performance for efficient, economical, and green reactions.

State-of-the-Art Advancements in Photocatalytic Hydrogenation: Reaction Mechanism and Recent Progress in Metal-Organic Framework (MOF)-Based Catalysts

Photocatalytic hydrogenation provides an effective alternative way for the synthesis of industrial chemicals to meet the economic and environment expectations. Especially, over the past few years, metal-organic frameworks (MOFs), featured with tunable structure, porosity, and crystallinity, have been significantly developed as many high-performance catalysts in the field of photocatalysis. In this review, the background and development of photocatalytic hydrogenation are systemically summarized. In particular, the comparison between photocatalysis and thermal catalysis, and the fundamental understanding of photohydrogenation, including reaction pathways, reducing species, regulation of selectivity, and critical parameters of light, are proposed. Moreover, this review highlights the advantages of MOFs-based photocatalysts in the area of photohydrogenation. Typical effective strategies for modifying MOFs-based composites to produce their advantages are concluded. The recent progress in the application of various types of MOFs-based photocatalysts for photohydrogenation of unsaturated organic chemicals and carbon dioxide (CO2 ) is summarized and discussed in detail. Finally, a brief conclusion and personal perspective on current challenges and future developments of photocatalytic hydrogenation processes and MOFs-based photocatalysts are also highlighted.

The photoreduction of selenite and selenate on the surface of few layer black phosphorus and a UiO-66 p–n junction heterostructure

The synthesis and characterization of a type-II heterojunction consisting of UiO-66 and few-layer black phosphorus with superior selenium oxyanion photo-reduction efficiency.