# Redox-Active Metal–Organic Framework Nanocrystals for the Simultaneous Adsorption, Detection, and Detoxification of Heavy Metal Cations

## TL;DR

This paper introduces redox-active metal-organic framework nanocrystals that can capture, detect, and detoxify heavy metals in water.

## Contribution

The study demonstrates how framework architecture and metal coordination influence adsorption, redox activity, and detection of heavy metals.

## Key findings

- Co-HHTP shows high uptake capacities for Cd²⁺, Hg²⁺, and Pb²⁺ due to its structural features.
- Co-HHTP enables redox-active capture by partially reducing heavy metal cations.
- MOF@textile composites retain adsorption efficiency and detect heavy metals at low concentrations.

## Abstract

The widespread contamination of water by heavy metals
requires
materials capable of efficient capture, in situ detoxification, and
real-time monitoring. This work examines a series of redox-active
metal–organic frameworks (MOFs) constructed from hexahydroxytriphenylene
(HHTP) ligands coordinated to cobalt, nickel, and copper (Co-HHTP,
Ni-HHTP, and Cu-HHTP), revealing how framework architecture and metal
coordination environment dictate adsorption capacity, redox activity,
and detection performance toward cadmium (Cd2+), mercury
(Hg2+), and lead (Pb2+) ions. Among the series,
Co-HHTP exhibits the highest uptake capacities of 169, 733, and 554
mg g–1 for Cd2+, Hg2+, and
Pb2+, respectively, attributed to its trigonal stacking
and intercalated layers that expose labile water-capped metal sites.
These sites facilitate electron transfer, enabling a redox-active
capture pathway in which heavy metal cations are partially reduced,
with concurrent oxidation of the HHTP ligand. In contrast, Cu-HHTP,
with an eclipsed stacking arrangement and limited redox complementarity
to the heavy metal ions examined, remains redox-inert and exhibits
the lowest performance. Deposition of Co-HHTP onto cotton, silk, and
polyester yields MOF@textile composites that retain adsorption efficiency
and enable rapid detection of heavy metals at low-ppm concentrations.
These findings establish a structure–function correlation,
emphasizing how stacking configuration, metal accessibility, and redox-active
ligands collectively govern multimechanistic heavy metal remediation.