Fe-doped NiCo2S4 catalyst derived from ZIF – 67 towards efficient hydrogen evolution reaction

Metal–organic frameworks (MOFs) are widely explored owing to their excellent nonlinear optical (NLO) properties. However, researchers have mainly focused on designing new structures of MOF crystals to adjust the NLO response while ignoring the influence of the number of metal–ligand coordination bonds on the NLO properties of MOFs. In this study, the influence of the coordination numbers of MOFs on their NLO properties is studied for the first time. Herein, MOFs with different coordination numbers, using trifluoroacetic acid as an auxiliary agent, are synthesized and their NLO properties are tested using the Z‐scan technique. The results reveal that the NLO absorption properties of MOFs with high coordination numbers can be effectively modulated from saturable absorption to reverse saturable absorption by increasing the excitation intensity. First‐principles calculations show that a change in the coordination numbers leads to a change in the charge transfer from metal to ligand, thereby resulting in different NLO responses. The MOFs with a high coordination number have potential applications in novel optical switches or logic gates. These results provide a reference for the precise adjustment of the NLO properties of MOFs.

Switchable Nonlinear Optical Absorption of Metal–Organic Frameworks

Metal–organic frameworks (MOFs) are a polymer hybrid family of compounds comprising metal ions that have been deliberately incorporated in organic ligands to form several multi-dimensional structures with unique structural and functional attributes. They have the typical properties of brittleness, major porosity, and randomly crystalline. These three factors hampered their potential incorporation into modern technologies. However, with the discovery of their polymers, hope was rekindled. Polymers, unlike their counterparts, are versatile and malleable and can be tailored into solids with a wide range of technical applications. MOFs can be effectively incorporated into polymer structures, resulting in polymers with enhanced properties and increased demand, according to recent studies. This review focuses on the synthetic procedures of MOFs used to create hybrid materials, as well as their potential environmentally related applications. Desalination, hazardous heavy metal removal and mitigation, gas and liquid separations and purifications, and dye removal will all be extensively discussed as applications. To assemble this review, we will add insight from recent papers and discoveries, as well as seminal reports from experts on the advancement of MOF-polymers.

Separation and remediation of environmental pollutants using metal-organic framework-based tailored materials.

Modulating Coordination Structures and Metal Environments of MOFs-Engineered Electrocatalysts for Water Electrolysis

This review addresses the most recent advances in the synthesis approaches, fundamental properties and photocatalytic activity of Cu3N nanostructures. Herein, the effect of synthesis conditions, such as solvent, temperature, time and precursor on the precipitation of Cu3N and the formation of secondary phases of Cu and Cu2O are surveyed, with emphasis on shape and size control. Furthermore, Cu3N nanostructures possess excellent optical properties, including a narrow bandgap in the range of 0.2 eV–2 eV for visible light absorption. In that regard, understanding the effect of the electronic structure on the bandgap and on the optical properties of Cu3N is therefore of interest. In fact, the density of states in the d-band of Cu has an influence on the band gap of Cu3N. Moreover, the potential of Cu3N nanomaterials for photocatalytic dye-degradation originates from the presence of active sites, i.e., Cu and N vacancies on the surface of the nanoparticles. Plasmonic nanoparticles tend to enhance the efficiency of photocatalytic dye degradation of Cu3N. Nevertheless, combining them with other potent photocatalysts, such as TiO2 and MoS2, augments the efficiency to 99%. Finally, the review concludes with perspectives and future research opportunities for Cu3N-based nanostructures.

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Surveying the Synthesis, Optical Properties and Photocatalytic Activity of Cu3N Nanomaterials

The design of an efficient electrocatalyst with controlled morphology and structural characteristics remain a challenging task for advanced electrochemical hydrogen evolution reaction (HER). Herein a simple method is utilized to improve the HER activity by introducing Fe/Pt bimetallic nanoparticles supported on highly porous carbon (PC) viz. one step carbonization of Nano‐MOF‐5(Zn) as precursor (metal organic framework). The as prepared Nano MOF‐5(Zn), Fe/Pt−PC and PC derived from MOF were characterized by various techniques like X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, BET (nitrogen adsorption/desorption isotherms) and Field emission scanning electron microscopy (FE‐SEM). The developed Fe−Pt/PC exhibits an optimal HER performance with low overpotential (85.4 mV) and a Tafel slope of 42.4 mV dec−1. The electrochemical results show that the developed material provides a viable approach for developing inexpensive Pt‐based catalyst for HER.

Nano-MOF-5 (Zn) Derived Porous Carbon as Support Electrocatalyst for Hydrogen Evolution Reaction

A wide variety of electrocatalysts has been evolved for hydrogen evolution reaction (HER) and it is reasonable to carry out HER with low cost electrocatalyst and a good efficiency. In this study, Cu3N was synthesized by nitridation of Cu2O and further utilized as an electrocatalyst towards HER. The developed Cu3N electrocatalyst was tested and results showed a low overpotential and moderate Tafel slope value (overpotential: 149.18 mV and Tafel slope 63.28 mV/dec at 10 mA/cm2) in alkaline medium with a charge transfer resistance value as calculated from electrochemical impendence spectroscopy being 1.44 Ω. Further from the experimental results, it was observed that the reaction kinetics was governed by Volmer-Heyrovsky mechanism. Moreover, Cu3N has shown an improved rate of electron transfer and enhanced accessible active sites, due to its structural properties and electrical conductivity. Thus the overall results show an excellent electrochemical performance, leading to a new pathway for the synthesis of low cost electrocatalyst for energy conversion and storage. 

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Muthumareeswaran Muthuramamoorty

Papers

Nano-MOF-5 (Zn) Derived Porous Carbon as Support Electrocatalyst for Hydrogen Evolution Reaction

Development of Cu3N electrocatalyst for hydrogen evolution reaction in alkaline medium