Incorporation of nanoparticles in the extraframework of MCM-41 and its effect on the photocatalytic degradation of phenol has been studied. Mesoporous MnO2 nanoparticles (meso-MnO2NPs) are incorporated in situ into the extraframework of MCM-41 during its synthesis to obtain mesoporous MnO2NPs-MCM-41(MM) materials. Three samples of mesoporous MnO2NPs-MCM-41 have been prepared with Si/Mn ratios 10, 50, and 90. The sample with Si/Mn ratio 10 shows better textural properties compared to the other two samples. Formation of meso-MnO2NPs, reversible coordination of Mn → Si, and formation the Fe-modified MM-10 nanocomposite (mesoporous Fe@MM-10 NC) are the crucial steps involved in the present investigation. The role of CTAB, NH3, and (NH4)2S2O8 are the key ingredients for the fabrication of meso-MnO2NPs and mesoporous Fe@MM-10 NC. The materials are characterized by LXRD, N2 sorption, and HRTEM to evaluate the mesoporosity, morphology, and textural properties. Mesoporous Fe@MM-10 NC was treated as an efficient photocatalyst for degradation of phenolic compounds, an exemplary move. Nearly 100% degradation of concentrated phenolic compounds (100 mg L-1) has been achieved within 45 min by mesoporous 5Fe@MM-10 NC. Intraparticle mesoporosity, small particle sizes of the nanocomposite, the formation of a large number of •OH radicals, and the generation of high photocurrent are important factors for swift degradation of phenolic compounds by mesoporous 5Fe@MM-10 NC material. © 2015 American Chemical Society.