Adsorption of volatile organic compounds in porous metal–organic frameworks functionalized by polyoxometalates

The functionalization of porous metal–organic frameworks (Cu3(BTC)2) was achieved by incorporating Keggin-type polyoxometalates (POMs), and further optimized via alkali metal ion-exchange. In addition to thermal gravimetric analysis, IR, single-crystal X-ray diffraction, and powder X-ray diffraction, the adsorption properties were characterized by N2 and volatile organic compounds (VOCs) adsorption measurements, including short-chain alcohols (C<4), cyclohexane, benzene, and toluene. The adsorption enthalpies estimated by the modified Clausius–Clapeyron equation provided insight into the impact of POMs and alkali metal cations on the adsorption of VOCs. The introduction of POMs not only improved the stability, but also brought the increase of adsorption capacity by strengthening the interaction with gas molecules. Furthermore, the exchanged alkali metal cations acted as active sites to interact with adsorbates and enhanced the adsorption of VOCs.

Graphical AbstractThe adsorption behavior of volatile organic compounds in porous metal–organic frameworks functionalized by polyoxometalates has been systematically evaluated.Figure optionsDownload as PowerPoint slideHighlights
► Functionalization of MOFs was achieved by incorporating Keggin-type POMs.
► Introduction of POMs improved the thermal stability and adsorption capacity.
► Alkali metal ion-exchange modified the inclusion state and also enhanced the adsorption.
► Adsorption enthalpies were estimated to study the impact of POMs and alkali metal cations.