Enhanced Catalytic Performance of N-Doped Carbon Sphere-Supported Pd Nanoparticles by Secondary Nitrogen Source Regulation for Formic Acid Dehydrogenation

The development of catalysts with high selectivity, good catalytic activity, and excellent cycle performance is of significance for the application of formic acid (HCOOH, FA) as a hydrogen support. Herein, Pd is deposited on a series of N-doped carbons, which are prepared by cocarbonization of N-containing zeolite imidazole frameworks (ZIF-8) and other N/C sources (melamine, xylitol, urea, and glucose), for hydrogen generation from FA. The results demonstrate that the introduction of a secondary N/C source further affects the catalytic performance of Pd by adjusting the morphology, specific surface area, N content, and type of carbon. The effects of N atoms and the favorable reaction pathways of FA dehydrogenation were revealed by theoretical calculation. This work will improve the understanding of N doping on the decomposition mechanism of FA and provide a new approach for the rational design of metal-N-C materials.

Hierarchical porous metal–organic gels and derived materials: from fundamentals to potential applications

This review summarizes recent progress in the development and applications of metal–organic gels (MOGs) and their hybrids and derivatives dividing them into subclasses and discussing their synthesis, design and structure–property relationship.

Porous carbon nanoarchitectonics for the environment: detection and adsorption

As a post-nanotechnology concept, nanoarchitectonics has emerged from the 20th century to the 21st century. This review summarizes the recent progress in the field of metal-free porous carbon nanoarchitectonics.

Recent advances on preparation and environmental applications of MOF-derived carbons in catalysis

Carbon materials derived from metal organic frameworks (MOFs) have excellent properties of high surface area, high porosity, adjustable pore size, high conductivity and stability, and their applications in catalysis have become a rapidly expanding research field. In this review, we have summarized the synthesis strategies of MOF-derived carbons with different physical and chemical properties, obtained through direct carbonization, co-pyrolysis and post-treatment. The potential applications of derived carbons, especially monometal-, bimetal-, nonmetal-doped and metal-free carbons in organo-catalysis, photocatalysis and electrocatalysis are analyzed in detail from the environmental perspective. In addition, the improvement of catalytic efficiency is also considered from the aspects of increasing active sites, enhancing the activity of reactants and promoting free electron transfer. The function and synergy of various species of the composites in the catalytic reaction are summarized. The reaction paths and mechanisms are analyzed, and research ideas or trends are proposed for further development.

MW Synthesis of ZIF-7. The Effect of Solvent on Particle Size and Hydrogen Sorption Properties

We report here fast (15 min) microwave-assisted solvothermal synthesis of zeolitic imidazolate framework material (ZIF-7). We have optimized solvent composition to achieve high porosity and hydrogen capacity and narrow particle size distribution. It was shown that synthesis in N,N-diethylformamide (DEF) results in a layered ZIF-7 III phase, while N,N-dimethylformamide (DMF) as solvent leads to a pure ZIF-7 phase in microwave conditions. A mixture of toluene with DMF allows the production of pure ZIF-7 material only with the triethylamine additive. Obtained materials were comprehensively characterized. We have pointed out that both X-ray diffraction and infrared spectroscopy could be used for the identification of ZIF-7 or ZIF-7 III phases. Although samples obtained in DMF, and in a mixture of DMF, toluene, and triethylamine were assigned to the pure ZIF-7 phase, solvent composition significantly affected the size of particles in the material and nitrogen and hydrogen adsorption process.

MOF derived ZnO/C nanocomposite with enhanced adsorption capacity and photocatalytic performance under sunlight

In this work, ZnO/C nanocomposites were obtained by calcining the prepared metal-organic framework precursor under nitrogen. The crystallinity and structure of the prepared products were characterized by XRD, FTIR, XPS and EDS. The morphologies of samples before and after calcination were observed by FESEM. The photocatalytic performances of ZnO/C were evaluated by the degradation of methylene blue under sunlight irradiation. Combined with DRS, PL and BET, the influence of calcination temperature on photocatalytic activities of as-synthesized zinc oxide were discussed as compared with commercial zinc oxide. The results indicated that ZnO/C composite obtained at 600 °C and 700 °C exhibited the superior adsorption capacity and photocatalytic activity. The possible photocatalytic mechanism of ZnO/C nanocomposite for degradation of MB under sunlight irradiation was proposed.

From metal-organic frameworks to porous carbon materials: recent progress and prospects from energy and environmental perspectives

Metal-organic frameworks (MOFs) have emerged as promising materials in the areas of gas storage, magnetism, luminescence, and catalysis owing to their superior property of having highly crystalline structures. However, MOF stability toward heat or humidity is considerably less as compared to carbons because they are constructed from the assembly of ligands with metal ions or clusters via coordination bonds. Transforming MOFs into carbons is bringing the novel potential for MOFs to achieve industrialization, and carbons with controlled pore sizes and surface doping are one of the most important porous materials. By selecting MOFs as a precursor or template, carbons with heteroatom doping and well-developed pores can be achieved. In this review, we discussed the state-of-art study progress made in the new development of MOF-derived metal-free porous carbons. In particular, the potential use of metal-free carbons from environmental and energy perspectives, such as adsorption, supercapacitors, and catalysts, were analyzed in detail. Moreover, an outlook for the sustainable development of MOF-derived porous carbons in the future was also presented.

Controlling the morphology of metal–organic frameworks and porous carbon materials: metal oxides as primary architecture-directing agents

We give a comprehensive overview of how the morphology control is an effective and versatile way to control the physicochemical properties of metal oxides that can be transferred to metal–organic frameworks and porous carbon materials.

Tunable and convenient synthesis of highly dispersed Fe-N x catalysts from graphene-supported Zn-Fe-ZIF for efficient oxygen reduction in acidic media

The development of low-cost, efficient and stable electrocatalysts for the oxygen reduction reaction (ORR) is desirable but remains a great challenge. We report a convenient and efficient synthesis approach of highly dispersed Fe–N_x catalysts for ORR. Typically, Fe–Zn-ZIF (zeolitic imidazolate frameworks) nanocrystals cast as precursor and graphene as supports, highly dispersed Fe–N_x species were fabricated with PVP (polyvinyl pyrrolidone) as surfactant via pyrolysis. With the help of graphene and surfactant, the agglomeration of iron particles has been avoided during pyrolysis, and the size and morphology of ZIF particles intercalating into the graphene layers can be regulated precisely as well. The amount of Fe–N_x active sites in C-rGO-ZIF catalyst arrived 4.29%, which is obviously higher than most monodispersed non-precious metal catalysts reported. The obtained C-rGO-ZIF catalyst exhibits a high onset potential of 0.89 V and a half-wave potential of 0.77 V, which is only 30 mV away from Pt/C in acidic media. The active sites of the catalyst was characterized and found to be the highly dispersed Fe–N_x species, large and accessible specific surface area of graphene and abundant active nitrogen atoms. When the C-rGO-ZIF catalyst was applied in the cathode of fuel cell, the power density can reach up to 301 mW cm⁻², which highlights a practical application potential on small power supplies.

A tunable and convenient synthesis approach of highly dispersed Fe–N_x catalysts for ORR in acidic media was reported.