Formation of Highly Selective Binding Pockets in UiO-Type MOFs From Bridged Linkers.
Metal-organic frameworks (MOFs) with precisely modified pore environments are essential for applications in catalysis, gas capture, and gas sensing. However, creating these highly selective sites through straightforward synthetic routes remains a challenge. Herein, we present a design strategy for UiO-type MOFs that enables control over the precise placement of functional groups within the tetrahedral pores of the framework, distinguishing it from less precise post-synthetic modification methods. By crosslinking two linker molecules with a short functional urea bridge pre-synthetically, the combination of the resulting linker geometry and the UiO-66 framework confines the crosslink to the trigonal pore windows. This results in pocket-like arrangements, as the urea bridges effectively "wall off" some of the pore windows. The structural implications are supported by modelling and electron crystallography. To demonstrate the functional versatility, we probe the selectivity of the obtained MOF toward aliphatic nitro compounds at low concentrations using vapor sorption measurements and compare it with other UiO-66 derivatives.