Metal–organic frameworks (MOFs) with core–shell structures enable to enhance intrinsic properties of constituent MOFs and impart additional functional activities. Although shell thickness is a key factor for regulating the properties of core–shell MOF particles, controlling it has been challenging. The widely used batch reactor synthesis cannot produce core–shell particles with uniform shell thickness because of poor reactant mixing. A microreactor could ensure excellent mixing, and that would allow to control shell thickness. In this study, we synthesized zeolitic imidazolate framework-8 (ZIF-8)@ZIF-67 and ZIF-67@ZIF-8 core–shell particles using a microreactor and investigated the effects of the mixing performance on the shell thickness of the obtained particles. Our results demonstrated that rapid mixing was critical for the uniformity of the synthesized particles. The concentration of core particles is another key factor that can preferentially induce heterogeneous nucleation on the surface of the core particles without inducing self-nucleation in the bulk solution, particularly when the self-nucleation rate of the shell MOF is high. The N₂ adsorption isotherms of the synthesized particles revealed their unique adsorption properties, which were ascribed to the core–shell structures obtained at low shell formation rates. Our simple and versatile synthesis technique not only allowed the preparation of ZIF@ZIF particles with novel functionalities but also can be extended to synthesize core–shell MOF particles with different combinations of core particles and shells.

中文翻译：

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沸石咪唑酸酯骨架（ZIF）@ZIF核壳金属有机骨架颗粒的流动微反应器合成及其吸附性能

具有核壳结构的金属有机框架（MOF）可以增强组成MOF的内在特性，并赋予其附加的功能活性。尽管壳的厚度是调节核-壳MOF颗粒性能的关键因素，但控制它仍然具有挑战性。由于不良的反应物混合，广泛使用的间歇式反应器合成不能产生具有均匀壳厚度的核-壳颗粒。微型反应器可以确保出色的混合，从而可以控制壳的厚度。在这项研究中，我们使用微反应器合成了沸石咪唑盐骨架8（ZIF-8）@ ZIF-67和ZIF-67 @ ZIF-8核-壳颗粒，并研究了混合性能对所得壳厚度的影响粒子。我们的结果表明，快速混合对于合成颗粒的均匀性至关重要。核心颗粒的浓度是另一个优先考虑的因素，可以优先在核心颗粒表面诱导异质形核，而不会在本体溶液中引起自形核，特别是当壳MOF的自形核速率高时。然后合成颗粒的_2个吸附等温线显示了其独特的吸附特性，这归因于在低壳形成速率下获得的核-壳结构。我们简单而通用的合成技术不仅允许制备具有新颖功能的ZIF @ ZIF颗粒，而且可以扩展为合成具有不同核颗粒和壳组合的核-壳MOF颗粒。