There has been a steady growth in research on porous materials such as metal–organic frameworks (MOFs) for their various applications. A significant drawback of conventional MOF synthesis is the use of toxic organic solvents to solubilize various organic linkers. Such an approach requires a longer MOF growth time and energy-intensive solvent recovery schemes during scale-up. In this work, we report the synthesis of Fe, Cu-based MOFs using trimesic acid (1,3,5-benzene tricarboxylic acid) as a linker via a facile aqueous medium route under environment-friendly conditions without requiring any toxic organic solvent and temperature. NaOH was used as a stoichiometric deprotonating agent for the aromatic carboxylic acid groups in the linker to facilitate linker solubility and interaction with metal ions. The aqueous medium-synthesized MOFs showed improved gas sorption characteristics compared with the same materials synthesized under the conventional solvent-mediated route. The synthesized MOFs were characterized by Brunauer–Emmett–Teller, powder X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, Fourier transform infrared, and X-ray photoelectron spectroscopy, and isotherms were measured for different gases (CO2, CH4, N2, propylene, and propane). Ideal adsorbed solution theory was used for binary selectivity calculations for gas systems such as CO2/CH4, CH4/N2, CO2/N2, C3H6/N2, and C3H6/C3H8. Density functional theory calculation was made to get an insight into the adsorptive behavior of the different gas molecules on the MOFs as adsorbent.