# Synthesis of Large‐Area 2D Prussian Blue as Ion‐Transport Channels for Non‐Volatile Memristors

## TL;DR

A new method creates large 2D Prussian blue films that work well in memory devices due to their efficient ion transport and structural stability.

## Contribution

A scalable synthesis method for high-quality, large-area 2D Prussian blue films with tunable thickness and excellent ion transport properties.

## Key findings

- The 2D Prussian blue films show reliable bipolar electrical switching with high Roff/on ratios and long retention.
- Ion transport across 1.5 µm lateral gaps was achieved, much larger than conventional distances.
- The synthesis method can be extended to other coordination polymers for various applications.

## Abstract

2D Prussian blue and its analogues hold great promise for applications in catalysis, energy conversion, sensing, and memory devices, thanks to their open frameworks, surface activity, and directional ion transport. However, synthesizing high‐quality and large‐area 2D films remains a major challenge. Here, we present a robust and scalable liquid‐liquid interfacial synthesis that enables the formation of continuous, 2D flakes of Prussian blue (Fe3+[Fe2+(CN)6]0.75) with tunable thicknesses from ∼2 nm to several hundred nanometers. The controlled reduction of [Fe3+(CN)6]3− to [Fe2+(CN)6]4− enables slow, directed growth of 2D‐FeFe layers. Unlike films formed from nanoparticles, this method yields high‐quality flakes suitable for integration into devices. As a demonstration, we incorporated these films into Ag filament‐based electrochemical metallization memristors. The 2D‐FeFe devices ≥50 nm thick exhibited reliable bipolar electrical switching, with high Roff/on ratios (∼106), >6 h retention, and stability over 150 cycles. Strikingly, switching was observed across 1.5 µm lateral gaps, far exceeding conventional silver filament formation distances, highlighting the superior ion transport and structural integrity of these 2D frameworks. This scalable approach to 2D Prussian blue, which has the potential to be extended to other related coordination polymers, offers exciting opportunities beyond memristors, enabling integration into technologies where thin‐film compatibility, directional ion transport, and high surface activity are critical, such as catalysis, energy storage, and neuromorphic computing.

A robust liquid‐liquid interfacial synthesis enables continuous, large‐area 2D Prussian blue films with tunable thickness from ∼2 nm to hundreds of nanometers. Controlled reduction guides slow, directional layer growth, yielding high‐quality flakes. These films show exceptional ion transport and device integration, demonstrated in memristors with long‐range switching, high Roff/on ratios, and strong cycling stability.