Computational and Experimental Assessment of CO2 Uptake in Phosphonate Monoester Metal–Organic Frameworks

Abstract

Phosphonate monoesters (PMEs) as ligands for metal–organic frameworks can potentially direct topology, enhance water stability, and modify pore chemistry. Here, we show, experimentally and computationally, not only that is the ratio of phosphonate to phosphonate monoester significant, but also that gas sorption depends on the distribution of the monoesters in the structure. A phosphonate monoester ligand, 1,3,5-tri(4-phosphonato)benzene-tris(monoethylester), was coordinated to copper(II) to form two different frameworks based on the same copper–phosphonate chain building units, one dense (1) and the other with an experimental surface area over 1000 m2 g–1 (CALF-33-Et3). One of the three phosphonate monoesters in CALF-33-Et3 can be hydrolyzed to make an isostructural material, CALF-33-Et2H, with approximately the same surface areas but vastly superior CO2 sorption. Controlling the hydrolysis at this site allowed the partially hydrolyzed variants, CALF-33-Et3–xHx (where 0 < x < 1), to be prepared and their ...