2D Covalent Organic Frameworks as Robust n-Type Organic Mixed Ionic-Electronic Conductors for Electrochemical Transistors.

Organic mixed ionic-electronic conductors (OMIECs) with exclusive electrochemical modulation and coupling between ions and electrons have exhibited intriguing efficiencies in bioelectronics, logic circuits, and wearable devices. However, OMIECs are typically linear polymers whose excessive structural swelling and morphological disorder during electrochemical doping led to low performance and instability. Here, we report n-type 2D covalent organic frameworks (2D COFs) as novel OMIECs (BTID-BFDO COF and BTDD-BFDO COF). The rigid π-conjugated scaffold functions as both a charge transport pathway and an ion-electron coupling plane, whilst the nanochannels serve as directional conduits for rapid ion transport. 2D OMIECs-based OECTs exhibit favorable threshold voltages (< 0.5 V), Ion/Ioff ratios (103) and high stability (modulation current retention rate of 91.3% during continuous operation) compared with the linear counterpart (< 10%). More importantly, we elucidate the mechanism underlying in situ ion transport and doping within the rigid porous architectures of 2D OMIECs, establishing a novel design paradigm for robust n-type organic semiconductors.