Metal Organic Nanocapsules as Two-Dimensional Network Building Blocks

Abstract

Metal−organic frameworks (MOFs) are a class of porous materials with a wide variety of applications, including molecular adsorption and separation. Recently, the first MOF based on the zincseamed pyrogallol[4]arene nanocapsule as a secondary building unit was reported. The zinc-seamed nanocapsules are linked together with 4,4′bipyridine, which is a divergent ligand commonly used in the synthesis of MOFs. In an effort to identify other likely candidates for nanocapsular linking, electronic structure calculations were performed to determine energetic and geometric properties of (Zn(C 2 O 2 H 3 ) 2 ) 1,2 Y model complexes, which have been shown previously to reliably model the zinc coordination sphere found in the nanocapsules. Here, Y represents one of 17 divergent ligands with N, S, or O electron-donating atoms. MOFs were synthesized and characterized from two of the ligands suggested as most suitable for further experimental study.

Coordination Polymers Constructed from Pyrogallol[4]arene-Assembled Metal–Organic Nanocapsules

“…Similarly, computational studies were performed on Zn-seamed dimeric CP-MONCs linked by a series of ligands (primarily cyclic systems with N, O, and S electron donor groups) . Computational data regarding BDEs between ligand and Zn-seamed MONCs were obtained using Gaussian09 and methods used previously. , The resulting calculations suggest that use of a tertiary amine is relatively favorable toward the formation of CP-MONCs using Zn-seamed dimeric MONCs as building blocks.…”

“…(a) Zinc-seamed dimeric CP-MONCs ( 3 ) connected by the ligand 1,2-bis­(2-pyridyl)­ethylene (BPE) and (b) CP-MONCs ( 4 ) connected by the ligand 1,4-bis­(imidazole-1-ylmethyl)­benzene (BIB). Reproduced with permission from ref . Copyright 2016 American Chemical Society.…”

“…Each nanometric capsule can be regarded as a metal "node", acting as a secondary building block in the coordination framework. 42,45,46 Interestingly, these CP-MONCs have some unique properties compared with traditional MOFs: (i) The porosity of CP-MONCs is derived from both the inner cavities of the MONCs and the external voids between MONCs. Sometimes the external voids are very small and can be ignored.…”

“…To date, studies on PgC-assembled MONCs have been focused on the synthesis of capsules by employing various metal ions or control of the internal volume of the MONCs (i.e., dimeric and hexameric capsules). ,,− Recently, a new discovery related to the modification of the exoligand on the surface of the MONCs is of great interest to us: these MONCs possess a large number of open metal sites on their exterior, making it facile to assemble MONCs into hierarchical coordination polymers. ,, Coordination polymers constructed from PgC-assembled MONCs (CP-MONCs) can be considered as another type of metal–organic framework (MOF) with higher complexity (Scheme ). Each nanometric capsule can be regarded as a metal “node”, acting as a secondary building block in the coordination framework. ,, Interestingly, these CP-MONCs have some unique properties compared with traditional MOFs: (i) The porosity of CP-MONCs is derived from both the inner cavities of the MONCs and the external voids between MONCs. Sometimes the external voids are very small and can be ignored.…”

“…Our group has been dedicated to the design and construction of CP-MONCs and has made considerable progress. − ,,,− In this Account, we will summarize the current status of CP-MONCs as prototypes in the field. Particular attention will be paid to the different topological structures derived from the various coordinate behaviors.…”