Acoustic manipulation of breathing MOFs particles for self-folding composite films preparation

[Display omitted] •A self-folding polymer film is preparated by acoustic manipulation of breathing MOFs particles.•Acoustic radiation force drives MOFs particles to form gradient distribution or microstructure.•The prepared polymer film exhibits self-folding in response to the acetone. Integrating breathing metal-organic frameworks (MOFs) particles into a passive polymer matrix is a successful strategy to develop self-folding composite films. However, the folding direction of the film depends on the gradient distribution of breathing MOFs particles in the polymer matrix, which is a huge challenge. Herein, acoustic manipulation is exploited to pattern breathing MIL-53(Fe) particles in liquid photosensitive resin to control over their spatial distribution, and combined with stereolithography to prepare self-folding composite films in situ. The prepared polymer film containing the microstructure of MIL-53(Fe) particles exhibits self-folding in response to the solvent that causes breathing of MIL-53(Fe) crystals. The reported strategy provides a simple, fast and environmentally friendly platform to prepare self-folding composite films based on breathing MOFs.