Achieve to easier opening of channels in anionic nanoporous metal-organic framework by cation exchange process

A zinc-based metal organic framework [(HDMA)(2)[Zn-3(BDC)(4)]center dot DMF center dot H2O) (1) (BDC2- is 1,4-benzenedicarboxylate, DMF is N,N-dimethylformamide and HDMA(+) is dimethylammonium), with C2/c space group, a = 33.299 (3), b = 9.790 (4), c = 18.185 (5) angstrom, alpha = gamma = 90.00 degrees, beta = 93.420 (6)degrees and V = 5918 (3) angstrom(3), was synthesized by solvothermal technique. Compound 1 was characterized by single crystal X-ray diffraction. It contains isolated zinc tetrahedra and octahedra by the organic linker BDC2- forming an anionic porous network with 2D channels. Positively charged ions and solvent molecules are present in the pores compensating for the negative charge of the framework. This positively charged molecule could be exchanged with metal ions, as it is evident by ICP, TGA and NMR studies. Unlike type V nitrogen adsorption isotherm curve of 1 at 77 K, replacement of the organic cation with smaller Li+ leads to a type I adsorption isotherm. (C) 2014 Elsevier Inc. All rights reserved.