Fabrication of pore window in ordered mesoporous silica by spatial control of functional groups

• Rod-shaped MCM41 crystals are multifunctionalized topographically.
• A functional pore window is fabricated around pore entrance.
• Location of pore window is confirmed by the distribution of window-complexed Pb species.
• The pore window could be bestowed with lock-and-key function.

Great difficulty has been found in controlling the spatial distribution of functional organic groups grafted onto ordered mesoporous silicas even though it plays a decisive role in many applications. Topographical multifunctionalization of rod-shaped MCM41 crystals has been accomplished in this study through selective surface fluorination and subsequent step-wise grafting of organic groups, leading to fabrication of a functional pore window on pore entrance surface. Distinctive fabrication of functional organic window around pore entrance was visualized by the distribution of window-complexed Pb cations in a narrow band within a distance of about 10–60 nm from both vertical crystal edges, pore entrances. Its unique function was clearly illustrated by interfacial property of the MCM41 crystals with both a guest molecule and a substrate surface. In particular, its lock-and-key function was successfully demonstrated by pH-dependent locking and unlocking of pore opening. Therefore, this study would contribite substantially to selective and precise manipulation of surface functionality in ordered mesoporous silica materials for tailor-making of diverse delivery vectors and nanoreactors.