Two-dimensional elastic molecular crystals via ZnF2 doping

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2024-11, Vol.499, p.156602, Article 156602
• Main Authors: Li, Shuzhen, Huang, Xueyong, Xing, Menghao, Yu, Jingqi, Du, Bingyao, Cao, Xiaoyu, Yan, Dongpeng
• Format: Article
• Language: English
• Subjects: Crystal engineering; Dynamic elasticity; Flexible-optical visualization; Two-dimensional (2D) molecular crystals
• ISSN: 1385-8947
• DOI: 10.1016/j.cej.2024.156602

•Two-dimensional (2D) elastic molecular crystals were synthesized and studied.•Mechanically bendable angle and fluorescence performance can be on-demand manipulated by a facile host–guest doping method.•ZnF2/TSB crystals exhibited excellent fluorescence quantum yield, up to 76.4%.•Mechanism behind the mechanical flexibility was established. Mechanically responsive and elastic crystals are emerging as one of promising smart systems in sensors, robotics, and photonic devices. Nevertheless, molecular crystals are generally rigid and tend to be broken under external forces, especially the doped crystals are more brittle due to lattice defects, making it difficult to achieve dynamic elasticity. Herein, we show a meaningful work to construct ZnF2 doping trans-1,2-diphenylethylene (TSB) optical materials, which achieve high elasticity of two-dimensional (2D) crystals under mechanical stress based on crystal engineering. Interestingly, the mechanically bendable angle and fluorescence performance of doping crystals can be on-demand manipulated as dual flexible-optical visualization through varying ZnF2 dopant. The optimized fluorescence quantum yield (76.4 %) and the bendable angle (180°) appear at initial molar doping ratios of 7.2 % and 18.0 % for ZnF2/TSB, respectively. Particularly, the crystals maintain bendable behavior even at rather low temperature of 77 K, which have not been reported for 2D flexible molecular crystals. Detailed crystal structure and computational analyses disclose the important roles of intermolecular interactions and corrugated packing patterns in elastic crystalline materials. This work therefore lays the foundation for finely manipulating dynamic elasticity and fluorescence properties towards designing next-generation flexible optical materials.