Continuous and reversible tuning of inter-layer spacings in two-dimensional conductive metal organic frameworks

Abstract

Understanding structure–property relationships in two-dimensional (2D) conductive metal–organic frameworks (2D cMOFs) is crucial for their targeted development and application in devices. Although valuable correlations have been identified by comparing 2D cMOFs with various metal and ligand compositions, inducing controlled structural transitions within a single 2D cMOF could offer more direct insights into these relationships. Herein, we report post-synthetic solvent removal as a straightforward strategy to achieve controlled structural contractions within octahedrally coordinated 2D cMOFs, demonstrating a continuous control of interlayer spacing from 3.45 to 3.27 Å. The addition of water to the contracted MOFs restored them to their pristine states while adding other solvents allowed for the isolation of materials with distinct interlayer spacings compared to their original state. These findings suggest remarkable reversibility and structural flexibility – characteristics typically observed in three-dimensional MOFs – now achieved in 2D cMOFs. Interestingly, electrical conductivity and optical band gap measurements across multiple samples revealed no correlation with interlayer spacing, raising the prospect for in-plane electron conduction as a dominant pathway in these materials. Overall, the post-synthetic control of interlayer spacing in 2D cMOFs described here opens promising avenues for focused exploration.