Methane, carbon dioxide and hydrogen storage in nanoporous dipeptide-based materials

Dipeptide crystalline materials are proposed for the absorption of environmentally and energetically relevant gases such as carbon dioxide, methane and hydrogen. The crystalline scaffolds, held together by a network of hydrogen bonds, of L-alanyl-L-valine (AV), L-valyl-L-alanine (VA), L-isoleucyl-L-valine (IV) and L-valyl-L-isoleucine (VI) form stable nanochannel pores with internal hydrophobic surfaces and suitable cross-section that encapsulates, efficiently and selectively, guest gases. The soft nature of the interactions guarantees reversibility of the process and triggered delivery simply by reducing gas pressure. With L-isoleucyl-L-valine, showing small channel diameter (3.9 Å), at 195K and already at 250 torr CO2 absorption reaches the value of 53 cm3 (STP) g_1 (90% maximum loading). We were able to attain remarkable CO2/CH4 selectivity even at atmospheric pressure, supporting the idea that this crystalline powder can find application in methane purification from carbon dioxide. Hydrogen showed a particular affinity for the IV and VI as shown by the adsorption isotherms run up to 10 atm and 77K. The type I Langmuir profile at 77 K reached maximum loading already at pressures close to 1 atm, and an absorption capacity of 52 cm3 (STP) g-1 for IV that corresponds to 0.5 mol/mol.