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

Abstract

Metal-organic frameworks (MOFs), {[Cu(2)(bdcppi)(dmf)(2)]·10DMF·2H(2)O}(n) (SNU-50) and {[Zn(2)(bdcppi)(dmf)(3)]·6DMF·4H(2)O}(n) (SNU-51), have been prepared by the solvothermal reactions of N,N'-bis(3,5-dicarboxyphenyl)pyromellitic diimide (H(4)BDCPPI) with Cu(NO(3))(2) and Zn(NO(3))(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 at 170 °C, adsorbs high amounts of N(2), H(2), O(2), CO(2), and CH(4) 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 CO(2) and CH(4) 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)]·7DMF·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.

Enhancing CO2 Separation Ability of a Metal–Organic Framework by Post‐Synthetic Ligand Exchange with Flexible Aliphatic Carboxylates

“…Such methods have been demonstrated to be effective in the introduction of functional groups, [10] the insertion, removal, or exchange of organic linkers, [7,8,11,12] as well as the exchange of framework metal ions. [9,13] To apply MOFs as carbon dioxide capture materials, they should have high CO 2 adsorption capacities and high selectivities for CO 2 adsorption over that of other gases such as CH 4 or N 2 . A high isosteric heat value for CO 2 adsorption generally leads to a high uptake capacity and increased selectivity for CO 2 adsorption over that of other gases, but a higher energy may be required for regeneration of the adsorbent.…”

Cyanide-bridged bimetallic multidimensional structures derived from organotin(IV) and dicyanoaurate building blocks: ion exchange, luminescence, and gas sorption properties

“…This complex adsorbs higher amounts (more than six times) of O 2 than N 2 at 77 K. Some cyanometallates also show high selectivity for oxygen over nitrogen [48]. This could be due to the fact that the unsaturated metal centers of the framework interact with O 2 more strongly than with N 2 [49]. Other cyano-bridged coordination solids containing coordinatively unsaturated metal centers have been shown to interact with H 2 at high loading [44,45].…”

Crystalline central-metal transformation in metal-organic frameworks

“…As mentioned above, a thermodynamically more stable coordination bond between the external metal ion and organic ligand is preferable in the CME process. Attempts to screen the external metal ion species were conducted by Suh et al, where the Zn II ions in the MOFs {[Zn 2 (BDCPPI)(DMF) 3 ]·7DMF·5H 2 O} n (26; BDCPPI = N,N -bis(3,5-dicarboxyphenyl)pyromellitic diimide) were exchanged completely and irreversibly for Cu II ions [112]. The exchange product still maintained the PtS-type network.…”