Microporous metal–organic frameworks: Synthesis and applications

Metal-organic frameworks (MOFs) have emerged as porous hybrid materials composed of metal ions and organic ligands. MOFs have attracted the attention of many researchers due to their promising characteristics, including high porosity, surface area, and drug loading capacity, tunable pore size and structure, good biodegradability and biocompatibility, and ease of functionalization. MOFs are categorized into three groups based on their pore widths, including microporous, mesoporous, and macroporous MOFs. MOFs with micropores have shown special features. The internal pore widths of microporous MOFs are less than 2 nm, which leads to their high porosity and surface area. Microporous MOFs could be synthesized through different strategies, including modulator-induced defect-formation, structure-directing agents, pillared-layer assembly, bridging helical chain secondary building units, coordination capabilities of P[dbnd]O moieties in the structure of a ligand, and using octahedral cage-like building units. Because of their unique properties, microporous MOFs have shown great potential for many applications such as separation, storage, catalysis, and sensing. A description of synthesis approaches and applications of microporous MOFs in recent years is provided in this review.