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.