Improvement of electron mobility of mesoporous PCN-600 single crystal microwires aligned via the steric hindrance effect

Abstract

One of mesoporous iron-based porphyrin metal-organic framework (MOF) materials, namely, PCN-600 exhibits one-dimensional channels, and features high stability in acid-base solutions and very high pore volume. It would be potentially applied in catalysis, lithium storage, solar cells, etc. However, when this material is prepared as a thin film, the thin film is usually un-oriented and its electron mobility is not strong enough. In this work, needle-like mesoporous PCN-600 single crystal microwires are first prepared via the solvothermal method with optimized synthesis procedure. Then, the acetone molecules adsorbed on the surface of adjacent PCN-600 microwires undergo the aldol condensation reaction under the catalysis of hydrochloric acid, and 4-hydroxy-4-methyl-pentanone-2 molecules are synthesized between adjacent PCN-600 microwires. Via the steric hindrance effect induced by 4-hydroxy-4-methylpentanone-2, the PCN-600 microwires are aligned to construct an array. Finally, the PCN-600 microwire array is transferred to an ITO substrate by a dipping method to form an oriented PCN-600 thin film. To demonstrate the feasibility of this oriented PCN-600 thin film applied in solar cells, its electron mobility is measured to be 117 ​cm2/Vs, which is twice that of poorly oriented film.