Interface-confined synthesis of a nonplanar redox-active covalent organic framework film for synaptic memristors.

The development of novel synthetic methodologies and unprecedented structures of covalent organic framework (COF) films is of great importance for exploring their potential applications in optoelectronic devices, sensors, and membrane separation. From the point of view of monomer selection, rigid building blocks are always the first choice for synthesizing crystalline COF films. However, the preparation of COF films with flexible building units remains challenging. Herein, by introducing flexible triphenylamine-based building units, a nonplanar COF film (TFPA-TAPA film) is fabricated via liquid-liquid interface-confined synthesis at room temperature and atmospheric pressure. The growth mechanism of the flexible building units at the liquid-liquid interface is related to the transformation of strip-type slices into free-standing COF films by dynamic covalent chemistry. As a proof-of-concept, the as-fabricated Al/TFPA-TAPA/ITO device shows excellent multilevel storage and history-dependent memristive switching behavior. The synaptic potentiation/depression, human learning and memorization functions, as well as the transition from short-term synaptic plasticity to long-term plasticity, are successfully emulated by using this synaptic memristor.