Review on Metal-Organic Framework Classification, Synthetic Approaches, and Influencing Factors: Applications in Energy, Drug Delivery, and Wastewater Treatment

Metal ions or clusters that have been bonded with organic linkers to create one- or more-dimensional structures are referred to as metal-organic frameworks (MOFs). Reticular synthesis also forms MOFs with properly designated components that can result in crystals with high porosities and great chemical and thermal stability. Due to the wider surface area, huge pore size, crystalline nature, and tunability, numerous MOFs have been shown to be potential candidates in various fields like gas storage and delivery, energy storage, catalysis, and chemical/biosensing. This study provides a quick overview of the current MOF synthesis techniques in order to familiarize newcomers in the chemical sciences field with the fast-growing MOF research. Beginning with the classification and nomenclature of MOFs, synthesis approaches of MOFs have been demonstrated. We also emphasize the potential applications of MOFs in numerous fields such as gas storage, drug delivery, rechargeable batteries, supercapacitors, and separation membranes. Lastly, the future scope is discussed along with prospective opportunities for the synthesis and application of nano-MOFs, which will help promote their uses in multidisciplinary research.

Conducting polymer-coated MIL-101/S composite with scale-like shell structure for improving Li–S batteries

Lithium–sulfur batteries are regarded as a promising energy storage system. However, they are plagued by rapid capacity decay, low coulombic efficiency, a severe shuttle effect and low sulfur loading in cathodes. To address these problems, effective carriers are highly demanded to encapsulate sulfur in order to extend the cycle life. Herein, we introduced a doped-PEDOT:PSS-coated MIL-101/S multi-core–shell structured composite. The unique structure of MIL-101, large specific area and conductive shell ensure high dispersion of sulfur in the composite and minimize the loss of polysulfides to the electrolyte. The doped-PEDOT:PSS-coated sulfur electrodes exhibited an increase in initial capacity and an improvement in rate characteristics. After 192 cycles at the current density of 0.1C, a doped-PEDOT:PSS-coated MIL-101/S electrode maintained a capacity of 606.62 mA h g⁻¹, while the MIL-101/S@PEDOT:PSS electrode delivered a capacity of 456.69 mA h g⁻¹. The EIS measurement revealed that the surface modification with the conducting polymer provided a lower resistance to the sulfur electrode, which resulted in better electrochemical behaviors in Li–S battery applications. Test results indicate that the MIL-101/S@doped-PEDOT:PSS is a promising host material for the sulfur cathode in the lithium–sulfur battery applications.

Lithium–sulfur batteries are regarded as a promising energy storage system.

Synthesis and Electrochemical Performance of SnOx Quantum Dots@ UiO-66 Hybrid for Lithium Ion Battery Applications

A novel method that combines the dehydration of inorganic clusters in metal-organic frameworks (MOFs) with nonaqueous sol-gel chemistry and pyrolysis processes is developed to synthesize SnO_x quantum dots@Zr-MOFs (UIO-66) composites. The size of as-prepared SnO_x nanoparticles is approximately 4 nm. Moreover, SnO_x nanoparticles are uniformly anchored on the surface of the Zr-MOFs, which serves as a matrix to alleviate the agglomeration of SnO_x grains. This structure provides an accessible surrounding space to accommodate the volume change of SnO_x during the charge/discharge process. Cyclic voltammetry and galvanostatic charge/discharge were employed to examine the electrochemical properties of the ultrafine SnO_x@Zr-MOF (UIO-66) material. Benefiting from the advantages of the smaller size of SnO_x nanoparticles and the synergistic effect between SnO_x nanoparticles and the Zr-MOFs, the SnO_x@Zr-MOF composite exhibits enhanced electrochemical performance when compared to that of its SnO_x bulk counterpart. Specifically, the discharge-specific capacity of the SnO_x@Zr-MOF electrode can still remain at 994 mA h g^-1 at 50 mA g^-1 after 100 cycles. The columbic efficiencies can reach 99%.

Enhanced catalytic activity and near room temperature gas sensing properties of SnO2 nanoclusters@mesoporous Sn(iv) organophosphonate composite

A simple route for preparing SnO₂ nanoclusters embedded on mesoporous Sn(iv) organophosphonate framework is described.

Nitrogen-doped-carbon-coated SnO2 nanoparticles derived from a SnO2@MOF composite as a lithium ion battery anode material

A facile method was developed to combine MOF-derived N-doped carbon with SnO₂ nanoparticles, which can cushion the volume change. The optimized SOC-3 composite achieved a reversible specific capacity of 1032 mA h g⁻¹ after 150 cycles at 100 mA g⁻¹.

Inorganic nanoparticles in porous coordination polymers

This review highlights studies on the synthesis, characterization, and functions of the inorganic nanoparticles in porous coordination polymers.