Enhanced Photocatalytic Activity in Thorium-Based Metal–Organic Frameworks (MOFs) via Solvent Induced π–π Stacking of Photoactive Ligands

Thorium-based metal–organic frameworks (MOFs) exhibit exceptional stability and hold promise for photocatalytic applications, yet their performance modulation remains challenging. Herein, two novel thorium MOFs ( IHEP-32 and IHEP-33 ) were synthesized via a solvent-induced strategy using N,N′-bis(5-isophthalic acid) naphthalene diimide (BINDI) ligands. Both materials demonstrate reversible photochromism and maintain structural integrity in aqueous solutions (pH 2–12). The results of the catalytic oxidation of thioether driven by visible light indicate that the catalytic conversion rate of IHEP-32 reached 73.3%, significantly higher than that of IHEP-33 at 50.2%. Structural analysis reveals that π–π stacking interactions between BINDI ligands in IHEP-32 facilitate efficient charge carrier transport, while the absence of such interactions in IHEP-33 limits its activity. This work offers valuable perspectives for designing innovative and efficient photocatalysts.