Metal-organic frameworks and their derivatives: emerging materials for energy conversion and storage

Metal-organic frameworks (MOFs) have received a lot of attention from scientists, becoming one of the fastest growing materials in chemistry and materials science in the past two decades. MOFs, also known as porous coordination polymers, are two- or three-dimensional porous crystalline materials with infinite lattices synthesized from secondary building units metal cation salts or clusters, and coordination-type linked multidentate organic ligands. MOFs, linking micro- and mesoporous materials, possess a superhigh surface area, up to 10000m2g−1 as measured by Brunauer-Emmett-Teller, much higher than zeolite and activated carbon. The combination of porous channels in MOFs with accessible sites possessing redox ability may enable a higher utilization efficiency of active sites than typical heterogeneous catalysts. At the same time, due to their flexible structure, MOFs can be tweaked by changing the properties of metal cations and linkers, as well as by postsynthetic modifications. Its clear and adjustable crystalline structure provides an ideal platform for the study of the structure-activity relationship of materials, which makes MOFs show great advantages both in basic research and practical application. Up to now, through the selection of various metal centers and organic ligands, more than 20,000 kinds of MOF materials have been synthesized, which have a very broad application prospect in many fields. The most utilized MOFs at present are MIL-53, HKUST-1, Fe-1,3,5-benzenecarboxylic acid, and zeolitic imidazolate framework-8. The characteristics of MOFs include drug delivery, heterogeneous catalysis, gas adsorption and separation, luminescence, and sensing. Therefore, MOFs are promising emerging multifunctional materials.