Liquid-Liquid interfacial approach for rapid synthesis of Well-Crystalline Two-Dimensional Metal-Organic frameworks for nitro reduction

Abstract

Two-dimensional metal–organic frameworks (2D MOFs) have garnered significant attention due to their exceptional properties across diverse research domains, including catalysis, biomedicine, gas adsorption, separation, energy storage, and sensing. Despite these promising attributes, the facile and large-scale synthesis of 2D MOFs with high crystallinity remains a formidable challenge. In this study, we propose a novel approach based on a modified liquid–liquid interfacial method for the rapid synthesis of well-crystalline 2D MOFs. By vigorously mixing water, a hydrophobic solvent, and an emulsifier, we generate micrometer-sized droplets that create substantial curved two-phase interfaces. This method is compatible with various ligands and metal ions, enabling the rapid formation of 2D MOFs at these curved interfaces under additional pressure. The subsequent separation of oil and water phases via centrifugal force promotes moderate π-π stacking within the 2D MOF, thereby stabilizing the lamellar structure and enriching the material at the two-phase interface. Remarkably, the entire synthesis process requires a mere 3 min, yielding grams of product in a single run. Furthermore, solvent reuse does not compromise the quality of the resulting 2D MOFs. As a practical application, we synthesized phthalocyanine (Pc)-based structures using this method for the catalytic reduction of nitroaromatics. Among these, Cu-CoPc (2D MOFs with Cu2+ coordinated to CoPc) emerged as the most active catalyst, achieving a turnover frequency (TOF) value of 4726 h−1 for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). Notably, this TOF value surpasses that of non-precious catalysts and is 180 times higher than that of commercial Pd/C (10 wt%).