Architecting X-Aggregates as Charge Transport Pathways to Enhance Photocatalytic Activity of Metal-Organic Frameworks

Metal-organic frameworks (MOFs) have demonstrated significant potential in photocatalysis. However, the impeded transport of charge carriers from the bulk to the surface creates a bottleneck that restricts the overall efficiency of photocatalytic reactions. To address this issue, in this study, charge carrier transport pathways are integrated into MOF photocatalysts by modulating the stacking arrangement of ligand chromophores. A series of MOFs featuring infinitely extended spiral pyrazinoquinoxaline-constructed π-columns are synthesized. The X-aggregate stacking mode of the pyrazinoquinoxaline chromophores not only prolongs the excited state lifetime but also enhances the efficiency of charge carrier transport (µ = 0.92 cm² V^-1 s^-1). One of these MOFs is successfully employed to catalyze the selective oxidation of a series of organic sulfides under visible light irradiation. Despite being nonporous, this MOF demonstrates activity comparable to that of reported porous organic framework photocatalysts. The findings of this study suggest that constructing a charge carrier transport pathway is a promising strategy for improving the performance of MOF-based photocatalysts.