High Gas Sorption and Metal-Ion Exchange of Microporous Metal-Organic Frameworks with Incorporated Imide Groups

Metal-organic frameworks (MOFs), {[Cu-2(bdcppi)(dmf)(2)]center dot 10DMF center dot 2H(2)O}(n) (SNU-50) and {[Zn-2(bdcppi)(dmf)(3)]center dot 6DMF center dot 4H(2)O}(n) (SNU-51), have been prepared by the solvothermal reactions of N,N'-bis(3,5-dicarboxyphenyl)pyromellitic diimide (H4BDCPPI) with Cu(NO3)(2) and Zn(NO3)(2), respectively. Framework SNU-50 has an NbO-type net structure, whereas SNU-51 has a PtS-type net structure. Desolvated solid [Cu-2(bdcppi)](n) (SNU-50'), which was prepared by guest exchange of SNU-50 with acetone followed by evacuation 170 degrees C, adsorbs high amounts of N-2, H-2, O-2, CO2, and CH4, gases due to the presence of a vacant coordination site at every metal ion, and to the presence of imide groups in the ligand. The Langmuir surface area is 2450 m(2)g(-1). It adsorbs H-2 gas up to 2.10 wt% at 1 atm and 77 K, with zero coverage isosteric heat of 7.1 kJ mol(-1), up to a total of 7.85 wt% at 77 K and 60 bar. Its CO2 and CH4 adsorption capacities at 298 K are 77 wt% at 55 bar and 17 wt% at 60 bar, respectively. Of particular note is the O-2 adsorption capacity of SNU-50' (118 wt% at 77 K and 0.2 atm), which is the highest reported so far for any MOF. By metal-ion exchange of SNU-51 with Cu-II, {[Cu-2(bdcppi)(dmf)(3)]center dot 7DMF center dot 5H(2)O}(n) (SNU-51-Cu-DMF) with a PtS-type net was prepared, which could not be synthesized by a direct solvothermal reaction.