A research team from the School of Materials Science and Engineering at Ocean University of China has developed a template-directed growth strategy to fabricate a 3D hierarchical superstructure of well-aligned bimetallic metal-organic framework (MOF) arrays, presenting a promising approach for electrocatalytic air sterilization. Their findings are published in the journal Engineering, detailing the design, characterization, and performance of the novel electrode material 0.3Co-MOF/Cu@Cu, which exhibits excellent water stability, conductivity, and catalytic activity for air sterilization applications.

To address the growing demands for low-cost and high-efficiency air sterilization technology amid increasing air pollution and bacterial contamination risks, the team focused on MOF-based materials, leveraging the advantages of bimetallic coordination and 3D hierarchical structural design. Copper mesh was selected as the substrate for its superior conductivity and permeability, with cobalt and copper introduced as metal coordination ions to construct the Co-MOF/Cu@Cu structure. Through density functional theory (DFT) calculations and electrochemical testing, 0.3Co-MOF/Cu@Cu was identified as the optimal material, showing better water stability and faster reaction kinetics compared with other formulations, as well as a higher content of Co³⁺ which contributes to structural stability.

Morphological and structural characterization confirmed that 0.3Co-MOF/Cu@Cu forms a wolf-tooth-shaped nanorod structure wrapped by thin nanosheets, with uniform element distribution and a crystal structure dominated by Co-MOF with minor copper doping. The material features a large specific surface area, a small charge transfer resistance, and a high electrochemical double-layer capacitance of 18.49 mF·cm⁻², indicating abundant exposed active sites and efficient electron transport. Chronopotentiometric measurements over 25 h at a current density of 10 mA·cm⁻² also verified its good stability and durability in alkaline medium.

Electrocatalytic air sterilization tests using Escherichia coli as the model Gram-negative bacterium were conducted at a relative humidity of 65%. At an air flow rate of 1.5 m·s⁻¹ and an alternating current voltage of 24 V, corresponding to a treatment time of just 0.0026 s, 0.3Co-MOF/Cu@Cu achieved a sterilization rate of 99.51%. The material’s sterilization mechanism relies on a combined effect of electroporation and reactive oxygen species (ROS) generation: The external electric field enhances the local electric field intensity of the 3D MOF structure, causing bacterial membrane electroporation, while oxygen vacancies on the material surface adsorb oxygen molecules and accelerate electrocatalytic reduction to produce superoxide anions (O₂⁻), the main ROS component. Exogenous ROS penetrate bacterial cells, and free electrons on the material surface disrupt bacterial physiological activities to induce endogenous ROS production, ultimately leading to bacterial death. Additionally, the generated ROS increases air negative ion concentration, potentially improving indoor air comfort.

The research demonstrates that the 3D hierarchical bimetallic MOF array electrode integrates structural and compositional advantages to realize high-efficiency air sterilization at low voltage with short treatment time, providing a new design reference for functional air sterilization materials and their practical application in indoor air purification systems such as air conditioners.

The paper “Template-Directed Growth of a 3D Hierarchical Structure of Well-Aligned Bimetallic MOF Arrays for High-Efficiency Electrocatalytic Air Sterilization,” is authored by Liting Dong, Shougang Chen, Zhipeng Zhao, Xiao Sun, Gaojian Lv, Wei Wang, Chengcheng Ma, Chunchao Hou, Wen Li, Jiakun Wang, Jianglin Gou. Full text of the open access paper: https://doi.org/10.1016/j.eng.2025.05.020. For more information about Engineering, visit the website at https://www.sciencedirect.com/journal/engineering.