Surface Curvature Dominated Guest-Induced Nonequilibrium Deformations of Single Covalent Organic Framework-300 Particles.

Understanding the guest-induced dynamic deformation process of covalent organic frameworks (COFs) is vitally important to further increase their stimulus-response performances. Here we report on the dark-field microscopic (DFM) imaging approach to in situ monitor the guest-induced deformation evolution of individual COF-300 crystals in real time. We observe not only transient and nonequilibrium intermediate deformation states but also local surface curvature-driven diverse adsorption behaviours of single COF-300 particles for dichloromethane (DCM), undergoing one, two, and multiple expansion-contraction deformations as well as contraction-to-expansion transition. The surface curvature-dominated deformations are ascribed to the significant differences in the adsorption capacity for DCM at the curved tip and flat side regions, in which DCM can be adsorbed preferentially by curved tip regions of COF-300.