Enhanced Carbon Dioxide Adsorption on Post-Synthetically Modified Metal-Organic Frameworks

Abstract

Four MOFs functionalized with 1-Me, 1-Pr, 1-Ph, and 1-PhCF3 were prepared through post-synthetic modifications of a metal-organic framework (MOF), UMCM-1-NH2 (1) with acetic, butyric, benzoic, and 4(trifluoromethyl)benzoic anhydrides, respectively. Methane adsorption measurements between 253 and 298 K at pressures up to 1 bar indicated that both 1-Ph and 1-PhCF3 adsorbed more CH4 than the parent MOF, 1. All the functionalized MOFs adsorbed more CO2 than 1 under conditions similar to the CH4 test. The introduction of functional groups promoted adsorption of both CH4 and CO2 despite significantly reducing Brunauer-Emmet-Teller (BET) surface area: 4170(1), 3550 (1-Me), 2900 (1-Pr), 3680 (1-Ph), and 3520 m(2)/g (1-PhCF3). Electron-withdrawing aromatic groups (1-Ph, 1-PhCF3) more effectively enhanced CO2 adsorption than electron-donating alkyl groups (1-Me, 1-Pr). In particular, 1-Ph adsorbed 23% more CO2 at 298 K and 50% more at 253 K than 1.