A novel, one-step synthesis of a highly stable mesoporous molecular sieve (MMS-H), which has a structure analogous to MCM-48 but which contains zeolite building units, is reported. A variety of experimental techniques -X-ray diffraction (XRD), N-2 adsorption/desorption, transmission electron microscopy (TEM), Fourier-transform infrared (FTIR) spectroscopy, hyperpolarized (XeNMR)-Xe-129, and solid-state Al-27 and P-31 magic-angle spinning (MAS) NMR spectroscopies -have been used to characterize the framework structure, porosity, and acidity of this novel mesoporous/microporous composite material, which is also found to possess superior thermal, hydrothermal, steam, and mechanical stabilities.