Structural diversity of metal–organic frameworks via employment of azamacrocycles as a building block

Research on incorporating macrocycles into metal–organic frameworks (MOFs) has been performed intensively due to the opportunities afforded by merging a merit of macrocycles with MOF chemistry, which lead to novel hybrid materials for potential application. Among the numerous kinds of macrocycles, azamacrocycles are used as traditional and popular chelating agents in supramolecular coordination chemistry, because they are very easily functionalized by joining pendant arms and possess a strong propensity to complex metal cations, accounting for the amine functionalities. With this as background, many types of azamacrocyclic MOFs have been synthesized, granting compositionally and topologically new MOFs. The macrocyclic rings can serve as additional adsorption sites or catalytic sites, and the pendant arms on the macrocycles can also play versatile roles such as structure-directing agents, pore-decorating moieties, or rotatable molecular gates for opening/closing pores. In this review, we comprehensively discuss the syntheses, structures, and features of azamacrocyclic MOFs reported to date. Based on representative studies, advantages of these compounds are described, such as how the azamacrocycles increase the structural diversity and complexity of the MOFs and induce novel structural properties within the architectures.