# Colored polymer-reinforced metal-organic framework microparticles with high charge-to-mass ratio for electrophoretic display

## TL;DR

Researchers developed colorful microparticles using metal-organic frameworks to improve electrophoretic displays with faster response and better stability.

## Contribution

Colored MOF microparticles reinforced with PEI offer superior electrophoretic performance and stability for color displays.

## Key findings

- MOF microparticles with PEI modification showed high Zeta potential and electrophoretic mobility.
- Response and recovery times were under 2.3 and 5.9 seconds under low field strength.
- Colored MOF microparticles outperformed traditional pigments in stability and display quality.

## Abstract

Besides high porosity and controllable structure, metal-organic framework (MOF) has some natural advantages for color electrophoretic particles: easy modification, controllable morphology, low and adjustable density, and high charge density, as well as rich, vivid, and stable colors. Therefore, we first integrated the four colored MOF microparticles and polyelectrolytes into the blue, reddish-brown, green, and purple electrophoretic particles to construct the two-color stable dispersions in nonpolar isododecane as the electrophoretic inks. Here, the surface modification of polyethyleneimine (PEI) chains based on non-covalent interaction rendered these MOF microparticles fully reinforced to ~+30 mV in Zeta potential and over 3.6 × 10−10 m2 V−1 s−1 in the electrophoretic mobility. Under the ultralow field strength of 0.02 V μm−1, all the response time and recovery time were no more than 2.3 and 5.9 s, respectively. Even after long-time or multiple driving, these MOF microparticles and their reflectance value still remained constant to some extent. By comparison, these colored PEI-reinforced MOF microparticles are superior to the other organic color pigments and inorganic particles, in response capability, charge-to-mass ratio, preparation method, production cost, and stability in color, particle, and display. It is anticipated to provide an innovative and promising technical path for color electrophoresis display.

Schematic diagrams on the preparation and the Color EPD tests of the colored PEI-reinforced MOF microparticles.