Using a hydrothermal reaction of SmCl3•6H2O, ZnBr2 and TPPS, a crystalline metalloporphyrinic compound (MPC), [SmZn(TPPS)H3O]n•2nH2O (1), was synthesized. The crystal structure of the MPC exhibits a condensed and robust 3-D porous open framework. We studied the adsorption and desorption isotherms for N2, H2 and CO2 conducted at 77 K and 273 K. They show different isotherms such as Type I, II and III isotherm behaviors. We found that low temperature is propitious for the title complex to adsorb more H2, but less N2. Compound 1 showed remarkably high selectivity for CO2-N2 separation, and good thermal stability. The temperature dependent magnetic susceptibility shows an antiferromagnetic-like behavior for 1.