Metal–organic–silica (MOS) nanocomposites of copper, silver nanoparticles, Cu²⁺, Ag¹⁺, propyl ethylenediamine linker and silica gel (Cu–PEDA–S, Ag–PEDA–S, Cu²⁺–PEDA–S and Ag¹⁺–PEDA–S) were prepared by surface chemical modifications. Silica surface was modified with propyl ethylenediamine functional groups (PEDA–S) followed by treatment with Cu²⁺ and Ag¹⁺ solutions to produce metal ion–ethylenediamine–silica nanocomposites (Cu²⁺–PEDA–S and Ag¹⁺–PEDA–S). Finally, the metal–organic–silica nanocomposites of Cu–PEDA–S and Ag–PEDA–S were formed by chemical reduction of the metal ion incorporating modified silica. The nanocomposites were characterized by CHN elemental analysis, FTIR, TGA, EDAX and transmission electron microscopy. The Cu²⁺ ion composite provides active sites for chemisorptions of 3.0 wt% water due to Cu complex formation. The metal nanocomposites show a high dispersion of uniform Cu and Ag nanoparticles through the silica support with diameter range from 5 to 20 nm. Thermal gravimetric analysis shows the improvement of CO₂ adsorption stability in the MOS nanocomposites and Cu–PEDA–S has CO₂ adsorption capacity of 28% and 100% higher than that for the PEDA–S and Cu²⁺–PEDA–S nanocomposites, respectively. The preparation procedure is simple and favourable for the synthesis of a variety of metal–organic–silica nanocomposites for application as catalysts in greenhouse gas removal and capture.