High supercapacitive performances of Cu-MOFs dominated by morphologies: Effects of solvents, surfactants and concentrations

Pyridine 3,5-dicarboxylate-based metal-organic frameworks as an active electrode material for battery-supercapacitor hybrid energy storage devices

Efficient energy storage and conversion is crucial for a sustainable society. Battery-supercapacitor hybrid energy storage devices offer a promising solution, bridging the gap between traditional batteries and supercapacitors. In this regard, metal-organic frameworks (MOFs) have emerged as the most versatile functional compounds owing to their captivating structural features, unique properties, and extensive diversity of applications in energy storage. MOF properties are governed by the structure and topological characteristics, which are influenced by the types of ligands and metal nodes. Herein, MOFs based on pyridine 3,5-dicarboxylate (PYDC) ligand in combination with copper and cobalt are electrochemically analyzed. Owing to the promising initial characterization of Cu-PYDC-MOF, a battery supercapacitor hybrid device was fabricated, comprising Cu-PYDC-MOF and activated carbon (AC) electrodes. The device showcased energy and power density of 17 W h kg -1 and 2550 W kg -1, respectively. Dunn's model was employed to gain deeper insights into the capacitive and diffusive contributions of the device. With their performance and versatility, the PYDC-based MOFs stand at the forefront of energy technology, ready to power a brighter future for upcoming generations.

Synthesis of hierarchical Cd-Ni-MOF micro/nanostructures and derived Cd-Ni-MOF/CdS/NiS hybrid photocatalysts for efficient photocatalytic hydrogen evolution

Hierarchical micro/nanostructures assembled from nanorods and nanosheets have become promising candidates for photocatalysis. In this work, a series of hierarchical Cd-Ni-MOF micro/nanostructures, assembled from nanosheets and nanorods, were fabricated via a two-step solvothermal process involving the partial replacement of Ni²⁺ with Cd²⁺ in the Ni-MOF-74 structure. Different morphologies were obtained by considering different volume ratios of DMF and ethanol as the solvent during synthesis. Hierarchical Cd-Ni-MOF-T/CdS/NiS hybrid micro/nanostructures were synthesized by Ni²⁺ and Cd²⁺ exchange of Cd-Ni-MOFs with S^2-. The as-prepared samples, which were composed of thin nanosheets alone, exhibited the best photocatalytic H₂ evolution rate of about 40.08 mmol g^-1 h^-1. The p-n junction between CdS and NiS was found to be beneficial for the migration of photogenerated electrons from the conduction band (CB) of NiS to the CB of CdS. The heterojunction between CdS and Cd-Ni-MOF-T further promoted the transfer of an electron from the CB of CdS to the CB of Cd-Ni-MOF-T. Thus, this study demonstrated that hierarchical Cd-Ni-MOF-T/CdS/NiS architectures have a large specific surface area, leading to significantly improved photocatalytic activity.

Morphology control through the synthesis of metal-organic frameworks

Designable morphology and predictable properties are the most challenging goals in material engineering. Features such as shape, size, porosity, agglomeration ratio significantly affect the final properties of metal-organic frameworks (MOFs) and can be regulated throughout synthesis parameters but require a deep understanding of the mechanisms of MOFs formation. Herein, we systematically summarize the effects of the individual synthesis factors, such as pH of reaction mixture, including acidic or basic character of modulators, temperature, solvents types, surfactants type and content and ionic liquids on the morphology of growing MOFs. We identified main mechanisms of MOFs' growth leading to different morphology of final particles and next systematically discuss the effect of miscellaneous parameters on MOFs morphology based on the main mechanisms related to the nucleation, growth and formation of final MOFs structure, including coordination modulation, protonation/deprotonation acting and modulation by surfactants or capping agents. The effect of microwaves and ultrasound employment during synthesis is also considered due to their affecting especially nucleation and particles growing steps during MOFs formation.

Graphene quantum dot-sensitized Zn-MOFs for efficient visible-light-driven carbon dioxide reduction

A new hybrid Zn-Bim-His-1@GQD nanoparticle has been successfully developed for high selectivity of CO₂ reduction to yield CH₄.