Application of the piperazine-grafted CuBTTri metal-organic framework in postcombustion carbon dioxide capture

Post-synthetic modification of H-3[(Cu4Cl)(3)(BTTri)(8)] or CuBTTri, where H(3)BTTri = 1,3,5-tris(1H-1,2,3-triazol-5-yl)benzene, with piperazine (pip) has yielded the grafted framework H-3[(Cu4Cl)(3)(BTTri)(8)(pip)(12)], pip-CuBTTri, which exhibits an improved CO2 uptake at pressures pertinent to postcombustion flue gas capture compared with the non-grafted material. In particular, the volumetric capacity of pip-CuBTTri was 2.5 times higher than that of CuBTTri at ca. 0.15 bar and 293 K. A chemisorption mechanism for CO2 adsorption was proposed on the basis of diffuse reflectance infrared spectra (DRIFTS) and the high initial isosteric heat of adsorption (-Q(st), approximate to 96.5 kJ/mol). Application of the Ideal Adsorbed Solution Theory (LAST) to a simulated mixture of 0.15 bar CO2/0.75 bar N-2 revealed a selectivity factor of 130. Both pressure and temperature swing processes were found to be suitable for facile regeneration of the material over multiple adsorption-desorption cycles. (C) 2013 Elsevier Inc. All rights reserved.