Metal Organic Frameworks
Metal Organic Frameworks, or MOFs, are a special type of crystalline material made by connecting metal ions or clusters with organic molecules. This creates a three-dimensional structure with a very large internal surface area and pores that can be finely adjusted in size. These materials act like molecular sponges, allowing them to catch, hold, or filter different molecules depending on their size, shape, and chemical properties. In the last ten years, MOFs have gained a lot of attention from scientists and industries because they have an extremely high porosity that is often better than zeolites and activated carbon, and because their chemical properties can be easily changed to suit different needs. Their ability to be modified makes them very versatile and useful in many areas, such as energy storage, cleaning up the environment, chemical reactions, gas separation, and other advanced material fields.
Properties of MOFs:
- Extremely High Surface Area: MOFs have very large surface areas, often over 5000 square meters per gram, which allows them to absorb or hold large amounts of gases and other molecules. This feature makes them very useful for storing and purifying gases.
- Tunable Pore Size and Architecture:The size and shape of the pores in MOFs can be controlled by selecting different metal ions and organic linkers. This allows creating pores of different sizes and shapes, which helps in selective absorption and tailored performance
- Adjustable Chemical Functionality: MOFs can be altered by adding chemical groups like -NH2, -COOH, and -SO3H, or by introducing sites that can speed up chemical reactions or resist or attract water. These changes help MOFs perform tasks like targeted chemical reactions, filtration, sensing, and separation more effectively.
- High Thermal and Structural Stability: Many modern MOFs, especially those based on zirconium or aluminium, are very stable when exposed to heat, moisture, and different chemicals. Their strong bonds between the metal and the organic parts make them durable, which is good for large-scale use in industries.
- Selective Adsorption Behaviour: Because of their designed pore structures and surface chemistry, MOFs can selectively capture certain gases like CO2, H2, CH4, VOCs, and heavy vapours. This selectivity is important for controlling the environment, purifying gases, and developing energy technologies.
- Lightweight and Crystalline Structure:MOFs are lightweight and have a well-ordered crystalline structure. This allows for precise engineering at the molecular level, which helps control their chemical and physical properties predictably
Applications of MOFs
Gas Storage and Separation : MOFs are used for storing and separating gases such as hydrogen, methane, carbon dioxide, and industrial vapours. Their high porosity and adjustable pore size make them far more efficient than activated carbon or zeolites, enabling technologies like clean energy storage, capturing carbon emissions, and purifying air.
Catalysis: MOFs work as advanced catalysts because their metal centres and organic linkers create active sites that speed up chemical reactions. They are used in converting CO2, refining petroleum, processing biomass, and in oxidation and reduction reactions for various industrial applications.
Environmental Remediation: MOFs are effective at removing harmful pollutants from water and air. They have a large surface area that allows them to quickly absorb heavy metals, toxic dyes, VOCs, hydrocarbons, and radioactive substances, making them useful in treating wastewater and cleaning up the environment.
Energy Storage and Conversion: MOFs and materials derived from them, such as porous carbons and metal oxides, improve the performance of batteries and supercapacitors. They help with ion movement, increase the capacity of electrodes, and improve the stability of batteries and fuel cells.
Biomedical Applications : Biocompatible and biodegradable MOFs are used for delivering drugs, treating cancer, imaging, and sensing. Their adjustable pore sizes allow for precise control over the release of medicines, and their flexible structures support targeted delivery within the body.
Sensing and Detection : MOFs are good at sensing because they show measurable changes in fluorescence, electrical conductivity, or structure when exposed to specific chemicals or biological molecules. They are used to detect gases, humidity, toxins, explosives, biological markers, and environmental pollutants with high sensitivity.
Chemical and Industrial Processing : MOFs are used in chemical purification, recovering solvents, drying gases, and separating hydrocarbons due to their selective adsorption ability. Their adjustable properties allow for specific molecule separation based on size and polarity.
Construction and Material Engineering (Emerging): MOFs are being explored for use in advanced coatings, anti-corrosion systems, fire-resistant materials, and building materials. MOF-derived nanomaterials improve the strength, durability, heat resistance, and UV protection in materials like polymers, bitumen, paints, and construction composites.
