Triethoxysilyl functionalized phenothiazinyl carbamates were synthesized and covalently grafted onto mesoporous MCM-41. XRD and N2 adsorption measurements indicated the presence of a highly ordered two-dimensional hexagonal structure of functional materials, while the incorporation of organic compounds in the solid materials was proven by means of 13C and 29Si solid-state NMR spectroscopy as well as by FT-IR spectroscopy. Upon oxidation with (NO)BF4, stable phenothiazine radical cations were generated in the pores of the materials, which can be detected by means of UV−vis and EPR spectroscopy.