Influence of the Solvent on the Assembly of Ni3(hexaiminotriphenylene)2 Metal-Organic Framework Nanosheets at the Air/Liquid Interface

Nanosheets of metal -organic frameworks (MOFs)(R) porous crystalline materials consisting of metal ions and organic ligands (R) are actively studied for their intrinsic chemical/ physical properties attributed to the reduced dimensionality and for their potential to function as ideal components of nano-devices, especially when electrical conduction is present. Air/ liquid interfacial synthesis is a promising technique to obtain highly oriented MOF nanosheets. However, rational control of size and shape combined with the aimed functionality remains an important issue to address making it necessary to research the critical factors governing nanosheet characteristics in the interfacial synthesis. Here, we investigate the influence of the solvent (R) methanol (MeOH) versus N,N-dimethylformamide (DMF)(R) used to prepare a ligand spread solution on an assembly of MOF nanosheets composed of Ni2+ and 2,3,6,7,10,11-hexaiminotriphenylene (HITP) (HITP-Ni-NS). We find that the macroscopic morphological uniformity in the micrometer scale is higher when DMF is used as the solvent. Regarding the microscopic crystalline domain, molecules of DMF with relatively high polarity and boiling point are involved in HITP-Ni-NS formation, hindering its growth and resulting in nanosheets with slightly smaller lateral size than that grown when MeOH is used. These findings provide crucial guidelines towards establishing a judicious strategy for creating desired MOF nanosheets at the air/liquid interface, thereby driving forward research on both fundamental and applied aspects of this field.