Growth Pattern Control and Nanoarchitecture Engineering of Metal-Organic Framework Single Crystals by Confined Space...

The nanoarchitecture engineering of metal-organic frameworks (MOFs) is a fascinating but intellectually challenging concept that opens up avenues for both tailoring the properties of MOFs and expanding their applications. Herein, we report the confined growth of ZIF-8 single crystals in a three-dimensionally ordered (3DO) macroporous polystyrene replica and reveal that their growth patterns, morphologies, and nanoarchitectures can be highly engineered using the concentration of the precursor. Impressively, the favorable in situ confined growth enables the successful fabrication of 3DO sphere-assembled ZIF-8 single crystals or 3DO single-crystalline ZIF-8 sphere arrays when a low- or high-concentration precursor solution, respectively, is used as the feedstock. Furthermore, our strategy can be extended to the preparation of other 3DO MOF single crystals, including ZIF-67 and HKUST-1, with similar controllable hierarchical nanoarchitectures. With the successful preparation of a series of diameter-tunable ZIF-8 single-crystalline spheres, we further unravel their interesting size-performance relationship in the Knoevenagle reaction between benzaldehyde and malononitrile, wherein the smallest spheres show the fastest first-order reaction kinetics. This study not only develops a general strategy for engineering the nanoarchitectures of MOF single crystals but also provides fundamental knowledge of the mechanism for the growth of hierarchical single crystals under confined spaces.