MOF

Metal-organic frameworks (MOFs) are porous crystalline materials composed of metal ions or clusters connected by organic ligands to form one-, two-, or three-dimensional networks. The modular nature of their building blocks enables reticular chemistry, allowing researchers to design frameworks with predetermined pore sizes, shapes, and functionalities. MOFs can exhibit very high surface areas and large internal pore volumes, enabling substantial adsorptive capacity per unit mass.

Most MOFs are synthesized by solvothermal or hydrothermal methods, using metal salts such as zinc, copper, or zirconium together with multidentate organic linkers like carboxylates or azolates. Notable classes include the copper-based HKUST-1, the zirconium-based UiO-66 family, and zeolitic imidazolate frameworks (ZIFs). Defect engineering, where missing linkers or nodes are intentionally introduced, can modify porosity and reactivity.

MOFs are valued for properties such as porosity, tunable pore sizes from sub-nanometer to several nanometers, and adjustable chemical environments within the pores. However, stability varies: many MOFs are sensitive to moisture or heat, while robust zirconium- and hafnium-based frameworks offer enhanced water and thermal stability.

Applications span gas storage and separation (hydrogen, methane, carbon dioxide), catalysis, carbon capture, sensing, drug delivery, and energy-related uses. Their design flexibility has made MOFs central to research in materials chemistry, catalysis, and environmental remediation. Ongoing challenges include improving stability under operational conditions, scale-up of synthesis, and cost reduction for industrial deployment.

The field emerged in the 1990s with the work of Omar Yaghi and colleagues, who coined reticular chemistry and demonstrated that a wide variety of frameworks could be built by assembling predefined metal nodes and linkers.