Framework flexibility and dynamic behavior are unique characteristics of metal-organic frameworks (MOFs). Gate-opening, as one of flexibility modes of MOFs, is mainly triggered by guest adsorption. The gate-opening feature of MOFs is influenced by the types of guest molecules, pressure, temperature and crystal size of MOFs. Gate-opening of MOFs led to an unexpected selectivity when used as adsorbents, as a result of guest-dependent gate-opening pressure. However, when MOFs were adapted for membrane separations, the framework flexibility sometimes can be disadvantage, resulting in the absence of sharp molecular sieving. This evokes considerable research efforts in recent years to suppress the negative impacts of framework flexibility, for example, hindering the gate-opening effects, on the gas separation performance of MOF membranes. Very recently, accurate regulation of gate-opening of MOF membranes by applying an external electric field was demonstrated, opening new scenario to develop MOFs with excellent performances for molecular separations.

框架的灵活性和动态行为是金属有机框架（MOF）的独特特征。作为MOFs的一种柔性模式，开门主要是由客体吸附引起的。MOF的开门特性受来宾分子类型，压力，温度和MOF晶体尺寸的影响。由于客体依赖的开门压力，当用作吸附剂时，MOF的开门会导致意外的选择性。但是，当MOF适用于膜分离时，骨架的柔韧性有时可能会很不利，从而导致分子筛的缺乏。这引起了近年来的大量研究努力，以抑制框架柔性对MOF膜的气体分离性能的负面影响，例如，阻碍开门效果。最近，