Metal organic framework (MOF)-based micro/nanoscaled materials for heavy metal ions removal: The cutting-edge study on designs, synthesis, and applications

The rapid industrial and agricultural expansion is arousing increasingly severe heavy metal ion pollution due to their high toxicity to human beings and detrimental effect on the environment and ecology. Therefore, heavy metal ion removal from wastewater is an urgent need which has become an important area of research in both academia and industry. Advanced material has been synthesized either to overhaul classical water purification methods or bring avant-garde system to overcome the challenges, such as improving cost efficiency, scalability, multiple metals removal, reusability etc. Metal-organic frameworks (MOFs), a new kind of three-dimensional organic–inorganic complex, have attracted incredible attention to satisfy these challenges, especially in the field of adsorption. This is due to their highly porous structure, extremely high surface area, and highly available exposed adsorptive sites. Remarkable progress has been done in this sector which urges a comprehensive, but critical review which could be substantial and easily readable. Here, we aimed to cover these cutting-edge research developments on design, synthesis, and applications of MOFs in effective heavy metals removal from water. We focused on high adsorption efficiency-oriented design and synthesis of MOF-based micro/nanoscaled materials including bulk MOF-based micro/nano materials (bulk MOFs, composites, and MOFs with unique nanostructures), two-dimensional (2D) MOF nanosheets, and three-dimensional (3D) MOFs incorporated porous membranes. The engineering principles of these structures for pollutants removal were corroborated and their performances were thoroughly compared. Based on our analysis and discussions, the most desirable characters of high-efficiency MOFs based adsorbents were revealed. We also scrutinized the knowledge gaps and gave future directions and perspectives for new experimental design. This review paper could provide some references and directions on the specific MOFs fabrication towards efficient heavy metal ions removal.