Solvent exchange as a synthetic handle for controlling molecular crystals

Organic/molecular crystals have been widely applied in medicine, imaging, explosives, and optoelectronics, but there are very limited methods for controlling their size and shape at the micro- or nanoscale. Herein, we develop solvent exchange as a new synthetic handle for creating complex morphologies in molecular crystals. With mitigated driving force in solution phase, solvent loss or exchange in C₆₀ plates does not lead to structural collapse, but leads to crystal transformation to mesh networks. C₇₀ and tetrakis(4-bromophenyl)ethylene crystals show similar transformation upon solvent exchange. We study the co-solvents and uncover their competing roles in the destabilization of the crystal structure and the on-site crystallization towards rods. This unconventional role of co-solvent is of importance not only for understanding the pore formation and crumbling, but also a new step towards regulating the desolvation and recrystallization processes. Rational transformation of organic crystals would open a new synthetic route for designing complex structures and new properties.