Modulating supramolecular binding of carbon dioxide in a redox-active porous metal-organic framework

Hydrogen bonds dominate many chemical and biological processes, and chemical modification enables control and modulation of host–guest systems. Here we report a targeted modification of hydrogen bonding and its effect on guest binding in redox-active materials. MFM-300(V(III)) {[V(III)(2)(OH)(2)(L)], LH(4)=biphenyl-3,3′,5,5′-tetracarboxylic acid} can be oxidized to isostructural MFM-300(V(IV)), [V(IV)(2)O(2)(L)], in which deprotonation of the bridging hydroxyl groups occurs. MFM-300(V(III)) shows the second highest CO(2) uptake capacity in metal-organic framework materials at 298 K and 1 bar (6.0 mmol g(−1)) and involves hydrogen bonding between the OH group of the host and the O-donor of CO(2), which binds in an end-on manner, [Image: see text]=1.863(1) Å. In contrast, CO(2)-loaded MFM-300(V(IV)) shows CO(2) bound side-on to the oxy group and sandwiched between two phenyl groups involving a unique [Image: see text]···c.g.(phenyl) interaction [3.069(2), 3.146(3) Å]. The macroscopic packing of CO(2) in the pores is directly influenced by these primary binding sites.