Tetrazole-based porous metal-organic frameworks for selective CO2 adsorption and isomerization studies

Tetrazole-based molecules are of numerous bridging coordination modes affording great synthetic possibilities for the preparation of porous metal-tetrazolate architectures for many applications, such as carbon captures. We reported here three tetrazole-based MOFs: 1, {[Cu12(ttz)8/3Cl5(H2O)16]11+·11Cl–}n (H3ttz = N2,N4,N6-tris(4-(1H-tetrazol-5-yl)phenyl)-1,3,5-triazine-2,4,6-triamine), contains highly positively charged Cu12 clusters and largest mesopores (32 A) in the reported MOFs based on tri-topic tetrazole ligand. 2 and 3 are two MOF isomers built by CuII and 2-(1H-tetrazol-5-yl)pyrimidine. 3 contains nonporous layers, while 2 contains 1D channel and showed high selectivity for adsorbing CO2, which should be attributed to the high density of free nucleophilic tetrazole N atoms on the pore surfaces. We found that the isomerization between 2 and 3 was caused by the diverse coordination mode of tetrazole-based ligand and can be controlled in the synthesis processes.