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

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 m²g^-1 (S_Langmuir 436 m²g^-1), high thermal stability (Td_onset = 300 °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 (α) with an increase in the permeability of CO₂ and H₂, 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 H₂/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.