Engineering Through-Bond to Through-Space Photoinduced Charge Transport Mechanism in 2D Metal Organic Frameworks via Ligand Aromatic Core Extension.

2-Dimensional (2D) photoconductive metal organic frameworks (MOFs), an emerging class of porous solids, have recently attracted great attention due to their potential applications in energy storage devices, chemiresistive sensing, and quantum information. However, the fundamental understanding of the factors that control their photoconductive mechanism remains underexplored, which significantly inhibits further development for these applications. In this work, we report a new strategy to controllably engineer their photoconductivity and charge transport (CT) pathway by systematically tuning the ligand size in 2D MOFs. Through a combination of hybrid synthesis, spectroscopic studies, and first-principles calculations, we show that extending the ligand from a single-benzene core to a 13-benzene core can effectively control both intralayer π-d orbital overlap and interlayer π-π stacking interaction. This not only significantly affects their photoconductivity but also shifts the CT pathway from a through-bond-dominated mechanism in smaller ligands to a through-space-dominated mechanism in larger ligands, providing a versatile design strategy for directional CT and opening new opportunities in photoelectronic and photocatalytic applications.