Dynamic organic crystals as exceptionally efficient artificial natural light-harvesting actuators

Dynamic organic crystal materials that can directly convert solar energy into mechanical work hold the potential to be efficient artificial actuators. However, developing dynamic organic crystals that can efficiently transform natural light energy into mechanical energy is still quite challenging. Herein, a novel dynamic organic crystal whose two polymorphs (Form I and Form II) are both capable of effectively converting natural light into work was successfully synthesized. Under the irradiation of ultraviolet (UV), blue and natural light, the on/off toggling of a photosalient effect could be triggered. Specifically, under UV light irradiation, Form I demonstrates output work densities of about 4.2-8.4 × 10⁴ J m^-3 and 1.6-4.9 × 10² J m^-3 before and after disintegration, respectively. Form II exhibits output work densities of about 1.3 × 10² to 1.9 × 10³ J m^-3 by means of photoinduced bending, suggesting that controllable bending may be more favorable for energy harvesting than the photosalient effect. Utilizing the exceptionally high energy transduction efficiency of Form I, we developed a natural light-driven micro-actuator that can realize output work densities of 2.8-5.0 × 10⁴ J m^-3. The natural light-harvesting performance of this actuator significantly surpasses those of previously reported photomechanical crystals and could even be comparable to thermal actuators.