Framework flexibility is one of the most important characteristics of metal-organic frameworks (MOFs),which is not only interesting,but also useful for a variety of applications.Desiguing,tailoring or controlling framework flexibility of MOFs is much more difficult than for static structural features such as the framework topology and pore size/shape.Nevertheless,with in-depth understanding of the relationship between framework flexibility and the host framework structure,guest loading and other aspects such as the crystal size/morphology and extemal physical environment,some strategies have been developed for controlling the flexibility of MOFs and the corresponding properties,which are summarized and discussed in this review.