ZIF-8/CNT Composites Prepared via Zinc-Functionalized Carbon Nanotubes

Integrating metal-organic frameworks like ZIF-8 with multi-walled carbon nanotubes (CNTs) is a powerful strategy to synthesize advanced catalytic materials with enhanced conductivity and structural stability. This work presents a multi-step synthesis of ZIF-8/CNT composites, focusing on a pre-anchoring zinc phase strategy onto the nanotubes to optimize interfacial interaction and template the framework growth.

CNTs were first functionalized using concentrated nitric acid under reflux to introduce oxygen-containing groups. A zinc precursor was then anchored onto the functionalized CNTs via NaOH precipitation followed by high-temperature calcination at 700 °C under argon to yield stable Zn/CNT matrices. Finally, ZIF-8 was grown in-situ on these matrices at room temperature for 24 h using 2-methylimidazole in methanol, targeting varying weight fractions.

XRD and FTIR analyses confirmed the successful room-temperature crystallization of ZIF-8(Zn) frameworks directly anchored onto the CNTs. The initial pre-zincification step significantly enhanced nanotube dispersion during the synthesis process. The BET surface area reached 1290 m²/g for the ZIF-8/CNT(1) composite. As the CNT mass fraction increased, the surface area predictably decreased (down to 620 m²/g for the CNT(10) variant). Furthermore, preliminary TGA profiling indicates that the integrated carbon scaffold successfully preserves and complements the thermal stability of the MOF structure.

A synthesis procedure for ZIF-8/CNT(1) composites was successfully developed, demonstrating that nanotubes act as effective nucleation centers, which significantly increased the process yield from 9% to 47%. XRD and FTIR analyses confirmed the MOF matrix's crystalline integrity and the successful formation of key Zn-N coordination bonds. Despite reducing the overall surface area, higher CNT content introduces mesopores that facilitate mass transport, enhancing the material's suitability for catalytic applications.