A novel composite adsorbent composed of an inorganic silica phase impregnated with a metal organic phase is synthesized and characterized. Specifically, MCM-41 is impregnated with copper active sites, which are then functionalized with benzene-1,3,5-tricarboxylic acid, which is the linker in the metal organic framework CuBTC. X-ray diffraction, nitrogen adsorption isotherms, thermogravimetric analysis, scanning electron microscopy, X-ray photoelectron spectroscopy, and equilibrium ammonia capacities are used to characterize the composite and control materials. Properties of the composite and control samples after conditioning at 85 °C in saturated water vapor for 5 h are also evaluated. Results show that the silica phase of the composite material provides an engineered phase that enhances the hydrothermal stability of the metal organic phase and the metal organic phase provides active sites for chemisorption. The composite material has a high ammonia capacity of 5.2 mol kg−1 and remains stable after conditioning. In comparison, the CuBTC structure degrades and shows low ammonia capacity after conditioning.