Towards Rational Modulation of In-Plane Molecular Arrangements in Metal-Organic Framework Nanosheets

A strategy to modulate the in-plane structural arrangement in preferentially oriented crystalline metal-organic framework (MOF) nanosheets assembled by a two-dimensional interfacial reaction between porphyrin units and metal ion linkers is reported. Starting with a tetratopic porphyrin MOF nanofilm, NAFS-2, the framework size and shape are modified by employing specially designed building units, a trans-ditopic and an expanded tetratopic porphyrin, and Cu2+ linkers. Reducing the number of binding parts affords a MOF nanosheet, NAFS-31, with a distorted in-plane structure. Extension of the peripheral substituents, while maintaining the tetratopic porphyrin geometry, results in marked unit cell size enlargement in an undistorted square grid in the MOF nanofilm, NAFS-41. The exquisite geometric control that these structural modifications entail is valuable to allow switching of chemical/physical properties of the nanosheets and lead to realization of their use in nanotechnological applications.