Non-macrocyclic molecular design enables cavity-adaptive cocrystals with high elasticity and low-threshold lasing.

The construction of cavity-adaptive cocrystals (CACs) based on linear non-macrocyclic π-conjugated hosts remains challenging due to their inherently weak and less predictable binding capabilities compared to conventional macrocyclic hosts. Here we overcome this limitation through the rational design and synthesis of CACs employing a structurally engineered non-macrocyclic host. This host combines a linear π-conjugated backbone with sterically hindered groups, allowing dynamic cavity modulation while maintaining its luminescent characteristics upon solvent and guest encapsulation. Heteroatom-modified guest molecules of similar size form molecular cavities with comparable dimensions yet exhibit different luminescence characteristics. Further tailoring the host's π-backbone yields color-tailorable CACs. These systems exhibit relatively strong intralayer C - H···π interactions coupled with weak interlayer forces, leading to high elasticity and low-threshold lasing action in single crystals and microcrystals. This work establishes a non-macrocyclic host/guest platform with adaptive cavities, demonstrating its potential as flexible laser emitters.