Cocrystal engineering is gaining interest across various disciplines since it can effectively tune the properties of solid substances via noncovalent synthesis by introducing new components into the lattice. Mechanochemistry is without a doubt the most valuable tool for the research of cocrystals, which combines the pursuit of efficient and sustainable process pathways with the exploration of supramolecular synthons that cannot be discovered using solution methods. In this review, concerning the significance of the mechanochemical synthesis of cocrystals, we begin by outlining the strategies for mechanochemical preparation of cocrystals. We then elaborate on the theoretical mechanisms of the mechanochemically induced formation of cocrystals and their polymorphs. On this foundation, several cross-fields in which mechanochemistry enhances the application value of cocrystal engineering are shown to overcome existing limitations, which are difficult or impossible to access using conventional solution methods. More importantly, we demonstrate that the introduction of new methods, such as cultivating single crystals from melt microdroplets, and new techniques, such as microelectron diffraction (Micro-ED), has harmoniously united the fields of cocrystal engineering and mechanochemistry. Finally, a brief conclusion and outlook are presented, including current challenges and future opportunities for the cooperation of mechanochemistry and cocrystal engineering.

The regulation of solid-state emission based on cocrystal engineering is an emerging strategy for developing next-generation luminescent materials. Here, three luminescent cocrystals (AA-DITFB, AA-TFTPA and AA-TCNB) of 9-anthraldehyde (9-AA) are reported, which exhibit a broad range of green-to-red emission. Tuning the photophysical properties of 9-AA via cocrystals is based on different mechanisms. Compared with single-component crystals, the difference in the emission properties of AA-DITFB and AA-TFTPA originates from the π–π interaction between chromophores. As for AA-TCNB, its prominent red-shifted emission is the result of the charge-transfer interaction, which is confirmed by infrared spectroscopy, “hole-electron” analysis and charge-transfer spectroscopy. This work not only reveals the relationship between molecular structure and fluorescent properties, but also proposes a strategy to develop multicolor luminescent systems with tunable efficiency and lifetime.

Thermosalient (TS) crystals have gained considerable attention due to their potential applications in various fields, including in actuators, sensors, energy harvesting, and artificial muscles. Herein, co-crystallization was employed to construct TS crystals by forming a twisted angle between aromatic rings. Two multicomponent trimethoprim (TMP) TS cocrystals, TMP-25HBA and TMP-OA, were obtained. Differential scanning calorimetry (DSC) and variable-temperature powder X-ray diffraction (VT-PXRD) revealed that TMP-OA undergoes a solid-to-solid phase transition, while TMP-25HBA does not exhibit any phase transition. To the best of our knowledge, TMP-25HBA is the first multicomponent TS crystal without phase transition. The TS effect of both crystals is a result of the unit cell’s anisotropic expansion.

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