Centre for Nanoporous Materials, School of Chemistry, The University of Manchester, Brunswick Street, M13 9PL, Manchester, UK.
Chemistry. 2013 Jun 17;19(25):8236-43. doi: 10.1002/chem.201300778. Epub 2013 Apr 26.
A new zeolitic-imidazolate framework (ZIF), [Zn(imidazolate)2-x(benzimidazolate)x], that has the zeolite A (LTA) framework topology and contains relatively inexpensive organic linkers has been revealed using in situ atomic force microscopy. The new material was grown on the structure-directing surface of [Zn(imidazolate)1.5(5-chlorobenzimidazolate)0.5] (ZIF-76) crystals, a metal-organic framework (MOF) that also possesses the LTA framework topology. The crystal growth processes for both [Zn(imidazolate)2-x(benzimidazolate)x] and ZIF-76 were observed using in situ atomic force microscopy; it is the first time the growth process of a nanoporous material with the complex zeolite A (LTA) framework topology has been monitored temporally at the nanoscale. The results reveal the crystal growth mechanisms and possible surface terminations on the {100} and {111} facets of the materials under low supersaturation conditions. Surface growth of these structurally complex materials was found to proceed through both "birth-and-spread" and spiral crystal-growth mechanisms, with the former occurring through the nucleation and spreading of metastable and stable sub-layers reliant on the presence of non-framework species to bridge the framework during formation. These results support the notion that the latter process may be a general mechanism of surface crystal growth applicable to numerous crystalline nanoporous materials of differing complexity and demonstrate that the methodology of seeded crystal growth can be used to discover previously unobtainable ZIFs and MOFs with desirable framework compositions.
一种新型沸石咪唑酯骨架（ZIF），[Zn（咪唑酯）2-x（苯并咪唑酯）x]，具有沸石 A（LTA）骨架拓扑结构且包含相对廉价的有机连接体，利用原位原子力显微镜揭示了这种新材料。该新材料在结构导向表面上生长[Zn（咪唑酯）1.5（5-氯苯并咪唑酯）0.5]（ZIF-76）晶体，这是一种具有 LTA 骨架拓扑结构的金属有机骨架（MOF）。使用原位原子力显微镜观察了[Zn（咪唑酯）2-x（苯并咪唑酯）x]和 ZIF-76 的晶体生长过程；这是首次在纳米尺度上监测具有复杂沸石 A（LTA）骨架拓扑结构的纳米多孔材料的生长过程。结果揭示了在低过饱和度条件下材料的{100}和{111}面的晶体生长机制和可能的表面终止。发现这些结构复杂的材料的表面生长通过“诞生和扩展”和螺旋晶体生长机制进行，前者通过亚稳和稳定子层的成核和扩展发生，这些子层依赖于非骨架物种的存在，以在形成过程中桥接骨架。这些结果支持这样一种观点，即后一种过程可能是表面晶体生长的一般机制，适用于具有不同复杂程度的众多结晶纳米多孔材料，并证明了种子晶体生长方法可用于发现以前无法获得的具有理想骨架组成的 ZIF 和 MOF。
