Macrocycle-based metal-organic frameworks

Organic struts incorporating macrocycles have been employed recently to construct extended metal-organic frameworks (MOFs), which opened up the possibility of forming hierarchically porous materials with two levels of porosity, i.e., one from the frameworks and the other one from the macrocycles. Integrating macrocycles into the MOF architectures not only leads to fundamental significance in merging the chemistry of MOFs with supramolecular chemistry, but also brings out novel properties from the hybrid materials obtained. This review summarizes recent developments of macrocycle-based MOFs by dividing them into several categories according to various macrocycles employed as the organic struts, including crown ethers, cyclodextrins, calixarenes, cucurbiturils, pillararenes and other macrocycles. The advantages and disadvantages of different macrocycles as the organic struts for building MOFs are compared and analyzed. In addition, five main applications currently developed using macrocycle-based MOFs are highlighted, which include (1) molecular recognition and separation, (2) gas adsorption and storage, (3) template synthesis, (4) nonlinear optics, and (5) heterogeneous catalysis. Perspectives and future challenges in this rapidly developing area are finally discussed.