Tuning the Host–Guest Interactions in a Phosphine Coordination Polymer through Different Types of post-Synthetic Modification

The porous Phosphine Coordination Material, PCM-10 contains abundant free P­(III) donor sites that can be subjected to a variety of post-synthetic modifications. The diverse P­(III)/P­(V) organic reactivity and coordination chemistry available to aryl phosphines have been exploited to decorate the pores of PCM-10, allowing for an extensive structure–function study. Polar PO moieties, charged P⁺–CH₃ phosphonium species with exchangeable coanions (I^–, F^–, BF₄^–, and PF₆^–) and P–AuCl groups have been successfully post-synthetically incorporated. These modifications directly affect the strength of the resulting host–guest interactions, as demonstrated by comparative sorption studies of CO₂, H₂, and other gases in the solid-state. Broad tunability of the enthalpy of CO₂ adsorption is observed: incorporation of BF₄^– ions inside the pores of PCM-10 results in 24% enhancement of the isosteric adsorption enthalpy of CO₂ compared to the parent material, while F^– anions induce a 36% reduction. Meanwhile, AuCl-decorated PCM-10 shows a high H₂ sorption capacity of 4.72 wt % at 77 K and 1.0 bar, versus only 0.63 wt % in the unmodified material.