Solid amine sorbents were prepared via cross-linking of polyamine compounds and polyaldehyde phosphorus dendrimers through a reductive amination approach. The CO2 adsorption capacities from inert gas streams and simulated flue gas were determined using a thermogravimetric analyzer (TGA) and a packed-bed reactor, (PBR) respectively. The sorbents adsorbed CO2 from inert CO2 gas streams up to 7.3 wt % at 65 degrees C and 10.7 wt % at 25 degrees C, while adsorbing CO2 from simulated flue gas up to 7.4 wt % at 65 degrees C. The amines are covalently bound in the sorbent, providing a robust material that is stable at elevated temperatures and does not leach upon exposure to moisture. The sorbents underwent extensive cycle testing, with no degradation observed up to 45 cycles on the TGA and up to 25 cycles on the PBR, while displaying rapid kinetics for both adsorption and desorption of CO2.