Electrical Regulation of CO₂ Adsorption in the Metal-Organic Framework MIL-53

Active regulation of pore accessibility in microporous materials by external stimuli has aroused great attention in recent years. Here, we show the first experimental proof that guest adsorption in a dielectric microporous material can be regulated by a moderate external E-field below the gas breakdown voltage. CO₂ adsorption capacity in MIL-53 (Al) was significantly reduced, whereas that of NH₂-MIL-53 (Al) changed insignificantly under a direct current E-field gradient of 286 V/mm. Ab initio DFT calculations revealed that the E-field decreased the charge transfer between the CO₂ molecule and the adsorption site in the MIL-53 framework, which resulted in reduced binding energy and consequently lowered CO₂ adsorption capacity. This effect was only observed in the narrow pore state MIL-53 (Al) but not in its large pore configuration. Our results demonstrate the feasibility of regulating the adsorption of gas molecules in microporous materials using moderate E-fields.