Structural heterogeneity and dynamics in flexible metal-organic frameworks

Summary Flexible metal-organic frameworks (MOFs), renowned for their stimuli-responsive structures, are rising smart materials. With the recent progress in synthesizing MOFs with structural heterogeneity (i.e., containing multiple types of pores that exhibit distinctive geometries and functionalities), the targeted control of dynamics at the pore level has become a new direction of flexible MOF design. In this review, by introducing the recent advances of flexible MOFs, we discuss shifts in the research field from using the whole material to functionalizing individual pores and exploiting their relationships for cooperative dynamic behaviors and unprecedented properties. Some recent examples with pore-dependent dynamics are discussed to provide new perspectives for developing highly functional flexible MOFs. Finally, the latest progress in characterizing structural dynamics at the pore level is summarized with directions proposed for further development for a complete picture of the opportunities and challenges in this area.