2D and 3D Metal–Organic Framework at the Oil/Water Interface: A Case Study of Copper Benzenedicarboxylate

Metal-organic framework nanosheets (MOF NSs) have drawn a lot of attention lately; however, the interfacial behavior of these 2D MOFs has rarely been investigated. Here, the partition and distribution of 2D NS and 3D nanoparticle (NP) of copper benzenedicarboxylate (CuBDC) at the oil/water interface are imaged by cryo-scanning electron microscopy. A layer of approximate to 20 nm NS-CuBDC is detected with a lateral orientation along the interface, which is attributed to the existence of relatively hydrophobic planes and hydrophilic edges in NS-CuBDC. The highly hydrophilic CuBDC localizes along the interface within the water phase. The self-assembly of NS-CuBDC is found to be a facile method to construct small cubical NPs. The exchange of water into CuBDC leads to super hydrophilic wettability. Ascribed to their amphiphilic properties, NP-CuBDC acts as sole stabilizer to form stable oil-in-water emulsions. Synchrotron-based computed tomography is used to characterize the 3D distribution of CuBDC in emulsions at room temperature. This work provides great insights in the fundamental study of MOFs at the oil/water interface and may lead to further development of ultrathin 2D MOF membranes.