Downsizing metal–organic framework (MOF) crystals into the nanoregime offers a promising approach to further benefit from their inherent versatile pore structures and surface reactivity. In this article, downsizing is referred to as the deliberate production of typical large MOF crystals into their nanosized versions. Here, we discuss various strategies towards the formation of crystals below 100 nm and their impact on the nano-MOF crystal properties. Strategies include an adjustment of the synthesis parameters (e.g., time, temperature, and heating rate), surface modification, ligand modulation, control of solvation during crystal growth and physical grinding methods. These approaches, which are categorized into bottom-up and top-down methods, are also critically discussed and linked to the kinetics of MOF formation as well as to the homogeneity of their size distribution and crystallinity. This collection of downsizing routes allows one to tailor features of MOFs, such as the morphology, size distribution, and pore accessibility, for a particular application. This review provides an outlook on the enhanced performance of downsized MOFs along with their potential use for both existing and novel applications in a variety of disciplines, such as medical, energy, and agricultural research.

将金属有机框架（MOF）晶体缩小为纳米结构提供了一种有前途的方法，可进一步利用其固有的通用孔结构和表面反应性。在本文中，小型化是指将典型的大型MOF晶体有意生产为纳米尺寸。在这里，我们讨论了形成低于100 nm的晶体及其对纳米MOF晶体特性的影响的各种策略。策略包括调整合成参数（例如，时间，温度和加热速率），表面改性，配体调节，控制晶体生长过程中的溶剂化和物理研磨方法。这些方法分为自下而上和自上而下的方法，对MOF的形成也进行了严格的讨论，并将其与MOF形成的动力学及其尺寸分布和结晶度的均匀性联系起来。缩减路线的这一集合使人们可以为特定应用定制MOF的特征，例如形态，尺寸分布和孔可及性。这篇综述提供了缩小的MOF的性能增强前景，以及它们在医学，能源和农业研究等各种学科中既有用途又有新颖用途的潜在用途。