Mesoporous amino-functionalized metal–organic framework thin films with the UiO-68 topology were grown in a highly oriented fashion on two different self-assembled monolayers on gold. The oriented MOF films were covalently modified with the fluorescent dye Rhodamine B inside the pore system, as demonstrated with size-selective fluorescence quenching studies. Our study suggests that mesoporous metal–organic frameworks are promising hosts for the covalent attachment of numerous functional moieties in a molecularly designed crystalline environment.