[Paper Review] Hybrid organic-inorganic two-dimensional metal carbide MXenes with amido- and imido-terminated surfaces

Chenkun Zhou, Di Wang+10 more|arXiv (Cornell University)|May 27, 2023

MXene and MAX Phase MaterialsMaterials Science3 citations

TL;DR

This paper introduces a new class of hybrid two-dimensional MXenes (h-MXenes) with amido- and imido-terminated surfaces, synthesized via surface functionalization of 2D transition metal carbides. The hybrid structure enables coherent optical coupling between organic and inorganic components and exhibits exceptional hydrolytic stability, offering a platform for tunable 2D functional materials with enhanced stability and interfacial engineering potential.

ABSTRACT

Two-dimensional (2D) transition-metal carbides and nitrides (MXenes) show impressive performance in applications, such as supercapacitors, batteries, electromagnetic interference shielding, or electrocatalysis. These materials combine the electronic and mechanical properties of 2D inorganic crystals with chemically modifiable surfaces, and surface-engineered MXenes represent an ideal platform for fundamental and applied studies of interfaces in 2D functional materials. A natural step in structural engineering of MXene compounds is the development and understanding of MXenes with various organic functional groups covalently bound to inorganic 2D sheets. Such hybrid structures have the potential to unite the tailorability of organic molecules with the unique electronic properties of inorganic 2D solids. Here, we introduce a new family of hybrid MXenes (h-MXenes) with amido- and imido-bonding between organic and inorganic parts. The description of h-MXene structure requires an intricate mix of concepts from the fields of coordination chemistry, self-assembled monolayers (SAMs) and surface science. The optical properties of h-MXenes reveal coherent coupling between the organic and inorganic components. h-MXenes also show superior stability against hydrolysis in aqueous solutions.

Motivation & Objective

• To develop a new class of hybrid 2D MXenes with covalently bound organic functional groups.
• To explore the integration of organic chemistry with inorganic 2D materials for enhanced surface tunability.
• To improve hydrolytic stability of MXenes in aqueous environments through covalent surface functionalization.
• To establish a framework for interfacial engineering in 2D functional materials using coordination chemistry and self-assembled monolayers.
• To investigate the optical and electronic coupling between organic and inorganic components in hybrid 2D systems.

Proposed method

• Surface functionalization of 2D transition metal carbides (MXenes) with amine- and imine-containing organic molecules to form amido- and imido-bonded hybrids.
• Employing coordination chemistry principles to stabilize organic ligands on inorganic MXene surfaces.
• Utilizing self-assembled monolayer (SAM) concepts to achieve controlled, uniform surface termination.
• Characterizing the resulting h-MXenes using spectroscopic and microscopic techniques to confirm covalent bonding and surface structure.
• Analyzing optical properties to assess electronic coupling between organic and inorganic components.
• Evaluating hydrolytic stability in aqueous solutions through comparative stability testing.

Experimental results

Research questions

• RQ1 How can amido- and imido-functional groups be covalently integrated onto 2D MXene surfaces to form stable hybrid structures?
• RQ2 What is the extent of electronic coupling between organic functional groups and the inorganic MXene lattice?
• RQ3 How does surface functionalization with amido/imido groups affect the hydrolytic stability of MXenes in aqueous environments?
• RQ4 To what degree do the optical properties of h-MXenes reflect coherent interaction between organic and inorganic components?
• RQ5 Can the integration of organic ligands via coordination and self-assembly principles yield structurally well-defined and stable 2D hybrid materials?

Key findings

• The synthesis successfully produced hybrid MXenes (h-MXenes) with amido- and imido-terminated surfaces, confirmed by spectroscopic analysis.
• Optical measurements revealed coherent coupling between the organic and inorganic components, indicating strong electronic interaction.
• h-MXenes demonstrated superior resistance to hydrolysis in aqueous solutions compared to conventional MXenes.
• The surface functionalization strategy enabled precise control over surface chemistry, combining principles from coordination chemistry and SAM formation.
• The hybrid structure maintains the intrinsic 2D morphology and electronic properties of MXenes while introducing tunable surface functionality.
• The work establishes a new class of 2D materials with enhanced stability and interfacial tunability for advanced functional applications.