# Versatile Photofunctionalization of Carbon Nanotubes via [4 + 2] Cycloaddition: A Facile Route to Hybrid Nanomaterials

## TL;DR

Researchers developed a versatile method to modify carbon nanotubes using light and a chemical reaction, enabling the creation of hybrid nanomaterials with tailored properties.

## Contribution

A general [4+2] photofunctionalization method for carbon nanotubes is introduced, allowing postfunctionalization and hybrid material synthesis.

## Key findings

- The [4+2] photofunctionalization method works on various carbon nanotubes and amines with different electronic properties.
- Functionalization degrees of 8–20% were achieved under optimized conditions without altering nanotube morphology.
- Postfunctionalization with polymer nanoparticles creates hybrid materials with enhanced properties.

## Abstract

The [4 + 2] photofunctionalization of carbon nanotubes of different characteristics, such as single‐walled carbon nanotubes (0.9 and 1.4 nm diameter) or multiwalled carbon nanotubes (10 nm diameter), with aryl cyclobutyl amines 3 of diverse nature in the presence of common organic photocatalysts is presented. Through a facile synthetic protocol, a series of modified amines 3 is prepared, which undergo a photocatalyzed oxidative ring opening to subsequently react with the nanotube wall. Under the best reaction conditions (Rhodamine B, white light‐emitting diode, 40 h), an 8–20% functionalization degree in the form of N‐cyclohexylamine moieties is achieved. The reaction is general with respect to the type of nanotube employed, the electronic characteristics of the amine (decorated with electron‐donating and electron‐withdrawing groups), and it is homogeneous throughout the whole nanotube particle without affecting the morphology of the samples, as demonstrated by the characterization techniques performed. In addition, the method allows for postfunctionalization treatments by the on‐surface hydrolysis of an ester‐modified aryl cyclobutyl amine and subsequent amidation with amino‐decorated organic polymer nanoparticles. Thus, a hybrid material with different properties compared to the simple composite is obtained using this photochemical carbon nanotubes functionalization.

A [4 + 2] photocycloaddition of aryl cyclobutyl amines on carbon nanotubes is presented. A photocatalyst oxidizes the cyclic moiety to generate an active species trapped by the nanotube π‐cloud. The method functionalizes nanotubes of different characteristics and is tolerant to different functional groups decorating the amine. Postfunctionalization treatments can be performed to synthesis of hybrid materials by bonding nanotubes and organic polymers.© 2025 WILEY‐VCH GmbH