Hybrid bimetallic metal-organic frameworks: modulation of the framework stability and ultralarge CO2 uptake capacity.

A series of isostructural hybrid bimetallic metal-organic frameworks (MOFs), Ni(x)M(1-x)-ITHDs [M = Zn(II), Co(II)], have been prepared via a conventional solvothermal reaction in the presence of varying mole ratios of Ni(II)/Zn(II) or Ni(II)/Co(II) mixed metal ions. While a critical amount of the doped Ni(II) ion (more than ≈0.2 mol fraction) is needed to have any enhancement of the framework stability of the hybrid bimetallic NixZn1-x-ITHDs, even a very small amount of the doped Ni(II) ion (≈0.1 mol fraction) produced a full enhancement of the framework stability of the hybrid bimetallic Ni(x)Co(1-x)-ITHDs. The highly porous and rigid Ni(x)Co(1-x)-ITHDs activated via a conventional vacuum drying process shows a Brunauer-Emmett-Teller specific surface area of 5370 m(2) g(-1), which is comparable to that of pure Ni-ITHD. The CO2 uptake capacities of Ni-ITHD and Ni(0.11)Co(0.89)-ITHD (2.79 and 2.71 g g(-1), respectively) at 1 bar and 195 K are larger than those of any other reported MOFs under similar conditions and the excess CO2 uptake capacity at 40 bar and 295 K (≈1.50 g g(-1)) is comparable to those of other MOFs, which are activated via the supercritical carbon dioxide drying process, with similar pore volumes.