CeO2-Supported Pt Catalysts Derived from MOFs by Two Pyrolysis Strategies to Improve the Oxygen Activation Ability

Recent advances in Metal Organic Framework (MOF)-based hierarchical composites for water treatment by adsorptional photocatalysis: A review

Architecting a desirable and highly efficient nanocomposite for applications like adsorption, catalysis, etc. has always been a challenge. Metal Organic Framework (MOF)-based hierarchical composite has perceived popularity as an advanced adsorbent and catalyst. Hierarchically structured MOF material can be modulated to allow the surface interaction (external or internal) of MOF with the molecules of interest. They are well endowed with tunable functionality, high porosity, and increased surface area epitomizing mass transfer and mechanical stability of the fabricated nanostructure. Additionally, the anticipated optimization of nanocomposite can only be acquired by a thorough understanding of the synthesis techniques. This review starts with a brief introduction to MOF and the requirement for advanced nanocomposites after the setback faced by conventional MOF structures. Further, we discussed the background of MOF-based hierarchical composites followed by synthetic techniques including chemical and thermal treatment. It is important to rationally validate the successful nanocomposite fabrication by characterization techniques, an overview of challenges, and future perspectives associated with MOF-based hierarchically structured nanocomposite.

Transformation of metal-organic frameworks with retained networks

Metal-organic frameworks (MOFs) are a class of crystalline porous coordination materials with systematically designable network structures and tunable properties, demonstrating great potential for applications in diverse fields. However, the generally poor stability of dynamic coordination bonds in MOFs hinders their practical applications in harsh environments. Although MOFs have been used as precursors and templates for the production of various derivatives with enhanced stability via thermal treatment, the extreme thermolytic conditions often destroy the network structures, consequently resulting in obvious decreases in porosity and surface areas with undesired characteristics. This feature article discusses the generally used pathways for the transformation of MOFs and the advanced fabrication methods for the production of various MOF-derived materials. We particularly emphasize the recent progress in the designed strategies for customization and derivation tailoring of MOFs, which could produce MOF-derived functional materials with remaining framework skeletons and inherited characteristics (surface area, porosity and properties) of the parent MOFs, exhibiting great promise for practical applications.

Construction of nanorod structure confined Pt@CeO2 catalyst by in-situ encapsulation strategy for low temperature catalytic oxidation of toluene

In this work, the Pt@CeO2 catalyst with the nanorod structure (Pt@CeO2-R) and the bunch structure (Pt@CeO2-B) were synthesized through in situ encapsulation strategy of Pt species in Ce-MOFs, respectively. It is discovered that the Pt@CeO2-R catalyst owned the best catalytic performance for toluene catalytic combustion, and this situation was mainly caused by the confinement of Pt nanoparticles in Ce-MOFs, which was related to the chemical state of Pt species, redox ability, and the amount of active oxygen species. Among them, the Pt@CeO2-R catalyst owns more Ce3+ species, rich Pt4+ species, and abundant active oxygen species due to the existence of confined structure, which were conducive to promote catalytic oxidation of toluene. In addition, the Pt@CeO2-R catalyst also exhibited more redox ability, which may speed up the catalytic reaction rates. On the contrary, the Pt/CeO2-R catalyst was synthesized through a simple impregnation method, and exhibited the poor activity for toluene catalytic combustion due to poor Pt4+ species and active oxygen species. Therefore, this work provides a feasible experimental basis for the study of different morphologies and encapsulated metal particles.

Influence of Co-Precipitation Agent on the Structure, Texture and Catalytic Activity of Au-CeO2 Catalysts in Low-Temperature Oxidation of Benzyl Alcohol

The aim of the study was to establish the influence of a co-precipitation agent (i.e., NaOH–immediate precipitation; hexamethylenetetramine/urea–gradual precipitation and growth of nanostructures) on the properties and catalytic activity of as-synthesized Au-CeO2 nanocomposites. All catalysts were fully characterized with the use of XRD, nitrogen physisorption, ICP-OES, SEM, HR-TEM, UV-vis, XPS, and tested in low-temperature oxidation of benzyl alcohol as a model oxidation reaction. The results obtained in this study indicated that the type of co-precipitation agent has a significant impact on the growth of gold species. Immediate co-precipitation of Au-CeO2 nanostructures with the use of NaOH allowed obtainment of considerably smaller and more homogeneous in size gold nanoparticles than those formed by gradual co-precipitation and growth of Au-CeO2 nanostructures in the presence of hexamethylenetetramine or urea. In the catalytic tests, it was established that the key factor promoting high activity in low-temperature oxidation of benzyl alcohol was size of gold nanoparticles. The highest conversion of the alcohol was observed for the catalyst containing the smallest Au particle size (i.e., Au-CeO2 nanocomposite prepared with the use of NaOH as a co-precipitation agent).