Naphthalene Tetrazole-Based Nickel Metal-Organic Framework as a Filler of Polycarbonate Membranes to Improve CO2 and H2 Separation

A tetrazole-naphthalene linker was used to prepare a nickel MOF (metal-organic framework) (NiNDTz) with interesting properties: a specific surface area S-BET of 320 m(2)g(-1) (S-Langmuir 436 m(2)g(-1)), high thermal stability (Td(onset) = 300 degrees C), and CO2 uptake of 1.85 mmolg(-1), attributed to the tetrazole groups to be used as fillers in gas separation membranes. The role of these groups was crucial in the mechanical properties of mixed membranes prepared using polycarbonate as a polymer matrix, providing a very homogeneous filler distribution and also in the gas separation properties since a simultaneous increase in permeability and selectivity was achieved, especially in the hybrid membrane containing 20% filler (PC@NiNDTz-20%). This membrane exhibited an excellent balance between permeability (P) and selectivity (alpha) with an increase in the permeability of CO2 and H-2, 177 and 185%, respectively, and improvements in the selectivity of these gases against greenhouse gases such as methane and ethylene (between 15 and 28% improvement). These results make this membrane competitive to deal with separations in which these gases are involved, and are of special interest for the H-2/CH4 separation since it clearly improves the performance of pure PC and no better PC-based membranes have been reported in the literature for this separation.