Herein, we exploit the well-known swelling behaviour of metal–organic frameworks (MOFs) to create a selffolding
polymer film. Namely, we show that incorporating crystals of the flexible MOF MIL-88A into a polyvinylidene
difluoride (PVDF) matrix affords a polymer composite film that undergoes reversible shape transformations upon exposure
to polar solvents and vapours. Since the self-folding properties of this film correlate directly with the swelling
properties of the MIL-88A crystals, it selectively bends to certain solvents and its degree of folding can be controlled by
controlling the relative humidity. Moreover, it shows a shapememory effect at relative humidity values from 60% to 90%.
As proof of concept, we demonstrate that these composite films can lift cargo and can be used to assemble 3D structures from
2D patterns. Our strategy is a straightforward method for designing autonomous soft materials with folding properties
that can be tuned by judicious choice of the constituent flexible MOF.
