Critical Role of CUS in the Au/MOF-808(Zr) Catalyst for Reaction of CO2 with Amine/H2 via N-Methylation and N-Formylation

Schiff Base-Mediated Dual Active Site Catalyst for Efficient N-Formylation of Amines with CO2

Using CO2 as the C1 source for N-formylation of amine is a crucial energy-storage pathway to address the greenhouse effect while generating high-value-added chemicals but is limited by the activation of inert molecules. Herein, a dual active site catalyst with high CO2 activation and dihydrogen dissociation capacity was fabricated by incorporating a Schiff base and Au nanoparticles (NPs) on silicon dioxide (SiO2). The modification of the Schiff base not only provides an alkaline environment for CO2 absorption but also stabilizes Au NPs in a small and highly dispersed state, which regulates the electronic density of the metal for excellent H2 cleavage. The Schiff base-mediated Au catalyst significantly increased the yield of N-formylmorpholine from 3.9% in unmodified Au/SiO2 to 83.3% without the addition of any other additives. This work provides a new avenue for designing multisite catalysts by supporting surface modification to achieve simultaneous activation of multiple target substrates for synergistic catalysis.

Poor/rich dual electron reaction centers promoting photo-Fenton synergistic removal of organic pollutants: Graphite carbon-modified copper ferrite

Controlling high recombination of photogenerated carriers and optimizing low cycling of metal valence states are the two key control steps in enhancing photo-Fenton oxidation. To achieve multiscale synergy of photo-Fenton degradation, graphite carbon-modified copper ferrite composites (C/CFO) with poor/rich dual electron reaction centers were synthesized through direct carbonization of Fe/Cu bimetallic organic frameworks. A novel photo-Fenton catalytic system was constructed by irradiating the Fenton reaction with visible light. The photo-Fenton degradation efficiency of C/CFO for tetracycline (100 mg‧L-1) was 93.69% ± 0.02%, and the degradation rate constant was 4.84 times higher than that of the control. Optimized preparation and catalytic conditions, ensured good cyclic stability and broad applicability of C/CFO. This excellent stability performance improvement can be attributed to the following main factors: (1) The introduction of graphite carbon not only increases the specific surface area of C/CFO, but also acts as a bridge between the dual electron reaction centers, facilitating the transfer of photogenerated electrons. (2) On the one hand, the electron-poor reaction centers Fe and Cu capture photogenerated electrons, accelerate the Fenton reaction, and realize the valence cycling of Fe and Cu. On the other hand, the electron-rich reaction centers (oxygen vacancies) act as active sites for H2O2 adsorption, which greatly accelerate the decomposition of H2O2. Overall, the synergy of dual electron reaction centers effectively promoted photo-Fenton oxidation.

Aerobic Oxidative Synthesis of Formamides from Amines and Bioderived Formyl Surrogates

Herein we present a new strategy for the oxidative synthesis of formamides from various types of amines and bioderived formyl sources (DHA, GLA and GLCA) and molecular oxygen (O2) as oxidant on g-C3N4 supported Cu catalysts. Combined characterization data from EPR, XAFS, XRD and XPS revealed the formation of single CuN4 sites on supported Cuphen/C3N4 catalysts. EPR spin trapping experiments disclosed ⋅OOH radicals as reactive oxygen species and ⋅NR1R2 radicals being responsible for the initial C-C bond cleavage. Control experiments and DFT calculations showed that the successive C-C bond cleavage in DHA proceeds via a reaction mechanism co-mediated by ⋅NR1R2 and ⋅OOH radicals based on the well-equilibrated CuII and CuI cycle. Our catalyst has much higher activity (TOF) than those based on noble metals.

Improving bioelectrochemical performance by sulfur-doped titanium dioxide cooperated with Zirconium based metal-organic framework (S-TiO2@MOF-808) as cathode in microbial fuel cells

The sulfur-doped titanium dioxide (S-TiO2) cooperated with Zirconium based on a kind of metal-organic framework (MOF-808) was successfully prepared as cathode catalyst (S-TiO2@MOF-808) of microbial fuel cell (MFC) by two-step hydrothermal reaction. The particle size was approximately 5 μm, and the spherical S-TiO2 particle was attached to the surface of MOF-808 as irregular block solid. Zr-O, C-O and O-H bond were indicated to exist in S-TiO2@MOF-808. When n (Zr4+): n(Ti4+) was 1: 5, S-TiO2@MOF-808 showed better oxygen reduction reaction (ORR). The introduction of S-TiO2 restrained the framework collapse of MOF-808, S-TiO2@MOF-808 showed much higher catalytic stability in reaction. The recombination of sulfur and TiO2 reduced the charge transfer resistance, accelerated the electron transfer rate, and improved ORR greatly. The maximum power density of S-TiO2@MOF-808-MFC was 84.05 mW/m2, about 2.17 times of S-TiO2-MFC (38.64 mW/m2). The maximum voltage of S-TiO2@MOF-808-MFC was 205 mV, and the stability was maintained for 6 d.

Introducing VO2+ Group in Phosphomolybdic Acid and Supporting on MOF-808 for Efficient Oxidative Desulfurization

Herein, by introducing a VO2+ group into the microstructure of phosphomolybdenic acid (PMA) and loading it onto MOF-808, a series of composite catalysts were obtained by reducing the V element with Vitamin C (ascorbic acid). V atoms exist in the secondary structural units of phosphomolybdic acid as [VO(H2O)5]H[PMo12O40]. Surprisingly, the VC-VO-PMA/MOF-808 completely removed DBT and 4,6-DMDBT from the simulated oil in 12 min. The EPR and XPS results verify the electronic structure and valence state of V4+ in the composites. The oxygen vacancy and V4+ generated by VC modification in VC-VO-PMA/MOF-808 have positive effects on the oxidation desulfurization (ODS) activity. Based on the design of the microstructure and electronic structure, this study provides a new paradigm for the development of readily available and efficient ODS catalysts.

Synthesis and characterization of PCN-222 metal organic framework and its application for removing perfluorooctane sulfonate from water

Poly- and perfluoro alkyl substances (PFAS) are a group of man-made, notoriously persistent, and highly toxic contaminants in the environment reported worldwide. Many adsorbents including granular activated carbon, graphene, biochar, zeolites, and clay minerals have been tested for PFAS removal from water, but most of these materials suffer from high cost and/or poor removal performance. Here, we synthesized, characterized, and examined the efficiency of PCN-222(Fe), a new porous metal organic framework (MOF) with high water stability, for adsorptive removal of a frequently occurring PFAS, perfluorooctane sulfonate (PFOS), from water. The adsorption isotherm and kinetic studies revealed high PFOS adsorption capacity of PCN-222 (2257 mg/g), with rapid PFOS removal rate (within 30 min). The structure of PCN-222 was unaffected in water in the pH range of 2-10 but disintegrated and lost its PFOS removal ability at pH > 10. The PFOS adsorption on PCN-222 was an endothermic reaction. Electrostatic attraction was a dominant mechanism for PFOS adsorption at < 1694 mg/g PFOS concentration, while hydrophobic interaction accompanied with hydrogen-bonding was responsible at ≥ 1694 mg/g PFOS concentration. The interlayer morphology of PCN-222 did not change due to increasing PFOS loading. The findings of this study demonstrated superior features of PCN-222 over other conventional adsorbents for its potential application in removing PFOS from contaminated water to reduce PFOS transfer from water to living organisms.

Exploring novel heterojunctions based on the cerium metal-organic framework family and CAU-1, as dissimilar structures, for the sake of photocatalytic activity enhancement

Ce-based metal-organic frameworks (Ce-MOFs) are excellent photocatalysts due to their high efficiency in charge transportation. The integration of this family with CAU-1 (CAU standing for Christian-Albrechts-University), as a MOF benefiting from its ultra-high surface area, can remarkably enhance the properties of the structure. This research includes four new heterojunctions, namely CAU-1/Ce-BDC-NH2, CAU-1/Ce-UiO-66, CAU-1/Ce-MOF-808, and CAU-1/Ce-BDC, prepared by an innovative method, and several characterization techniques were employed to study the structural features of the frameworks. Their high surface area and low bandgap energy seemed appropriate for catalytic applications. Therefore, CAU-1/Ce-BDC was chosen for the photocatalytic removal of Cr(vi), a dangerous heavy metal, from aqueous systems. According to the results, a 96% reduction of Cr(vi) to Cr(iii) within 75 min was observed, and the catalyst retained its stability after four runs of reactions under acidic conditions.

Two-Dimensional Nanostructures in the World of Advanced Oxidation Processes

Two-dimensional compounds with nanostructural features are attracting attention from researchers worldwide. Their multitude of applications in various fields and vast potential for future technology advancements are successively increasing the research progress. Wastewater treatment and preventing dangerous substances from entering the environment have become important aspects due to the increasing environmental awareness, and increasing consumer demands have resulted in the appearance of new, often nonbiodegradable compounds. In this review, we focus on using the most promising 2D materials, such as MXenes, Bi2WO6, and MOFs, as catalysts in the modification of the Fenton process to degrade nonbiodegradable compounds. We analyze the efficiency of the process, its toxicity, previous environmental applications, and the stability and reusability of the catalyst. We also discuss the catalyst’s mechanisms of action. Collectively, this work provides insight into the possibility of implementing 2D material-based catalysts for industrial and urban wastewater treatment.

Fabrication of a novel heteroepitaxial structure from an MOF-on-MOF architecture as a photocatalyst for highly efficient Cr(vi) reduction

Ce-on-Zr-MOF-808, a novel MOF-on-MOF hybrid used for efficient chromium reduction under visible-light irradiation.

Amorphous zirconium metal-organic frameworks assembled from mixed porphyrins as solvent-free catalysts for Knoevenagel condensation

Three mixed porphyrins, icpp (1–3) were synthesized via the reactions of 4-formylbenzoic acid and 4-imidazolecarboxaldehyde in different proportions, and then five amorphous or crystalline Zr-MOFs—SPUZ (1–5) were obtained from icpp...

A density functional theoretical study on the stability of Pt clusters in MOF-808

Metal organic framework (MOF)-encapsulated metal clusters have shown superior catalytic activity due to geometric and electronic properties of metal clusters, which are largely determined by adsorption sites and sizes and morphologies of encapsulated metal clusters. In the present work, anchoring sites, the stability, and the agglomeration probability of Ptn (n = 1-23) clusters over an MOF-808 framework structure were studied using density functional theory calculations and ab initio molecular dynamics simulation. It has been found that Ptn (n = 1-7) clusters bind more strongly at the Zr6 metal node sites than at the interface and linker sites. Upon adsorption, significant amounts of electrons (+0.92 to +1.96 |e|) are transferred from Ptn clusters to the MOF framework. The agglomeration of single Pt1 atoms at the Zr6 metal node to form a Ptn cluster is unlikely, while the agglomeration at the interface or the linker is energetically feasible. Compared with the single Zr6 node, the bonding of Ptn clusters with two Zr6 metal nodes is weaker, with less electron (+0.12 to +0.89 |e|) transfer. Finally, our calculations show that CO adsorption at the single Pt atom is stabilized at the interface site, preventing its further agglomeration with Ptn clusters between the two Zr6 metal nodes.