We present a combined theoretical and experimental study on weak chemical complexation between PH3 and a few selected Cu(I)- and Al-based ionic liquids (ILs). PH3 molecules were found to covalently bind with the cationic sites of the ILs. Effects of cations, anions, ion pairing, and solvents on the binding strength were systematically examined. The weak coordination of PH3 on the ILs allows the PH3 gas to be stored at near ambient conditions with a high capacity.