Altering the Thermodynamics of Stimuli-Responsive Derivatives through Layered Hybrid Material Design

Adaptive (2D) materials with on-demand, tailored properties are a powerful concept that can be applied in next-generation optoelectronic devices, switchable heterogeneous catalysts, or multilevel data encryption systems. This work addresses current challenges associated with restricted/irreversible isomerization of photochromic moieties integrated within 2D materials via a novel strategy that leverages the tailoring of scaffold flexibility of two model material classes: metal-organic frameworks (MOFs) and perovskite-based materials. In particular, we demonstrate that flexible aliphatic groups, acting as "molecular grease", can reduce interactions between neighboring stimuli-responsive moieties within 2D layers, resulting in novel well-defined 2D crystalline materials with configurational freedom necessary for photoisomerization of confined "switches". To the best of our knowledge, this work unlocks a previously inaccessible class of photochromic materials containing high-energy Z isomers stabilized through "switch"-(2D) material cooperativity. Our synthetic strategy also allows for pressure-driven azobenzene isomerization without use of additional excitation sources, thereby broadening the applicability of azobenzene-based materials for device development. Moreover, the first analysis of photoswitch kinetics in perovskite-based materials is presented, showcasing the developed synthetic strategy's ability to provide sufficient material flexibility to promote "solution-like" photoisomerization rates of azobenzene derivatives. Overall, the design strategies herein allow for the preparation of 2D adaptive materials whose properties could be reversibly controlled via light and demonstrate how 2D confinement can shift the thermodynamic landscape of photochromic materials, favoring the stabilization of high-energy isomers that have not been reported to be stable in solution or existing materials to date.