Enhancing selective adsorption of CO2 through encapsulating FeTPPs into Cu-BTC

Efficient capture and separation of CO2 from flue gas and natural gas are highly promising to reduce carbon emissions and promote fuel calorific value. Here, a novel adsorbent (FeTPPs@Cu-BTC) for CO2 separation was synthesized by encapsulating 5, 10, 15, 20-tetrakis (4-sulfonatophenyl) porphyrinato iron (III) chloride (FeTPPs) into the cages of Cu-BTC through an in-situ packaging strategy. Such strategy efficiently overcomes the shortcoming of pore clogging and leaching induced by incorporating guest molecules through the wet impregnation method. Meanwhile, more tunable micropores and extra affinity sites for CO2 adsorption were created after encapsulation of FeTPPs, which preferably enhanced the CO2 uptakes of FeTPPs@Cu-BTC under low pressures and promoted the separation performances for CO2/N2 (15:85, v/v) and CO2/CH4 (50:50, v/v) mixtures. The corresponding selectivity of FeTPPs@Cu-BTC calculated by ideal adsorbed solution theory (IAST) respectively increase to 57.7 and 14.0 from 36.0 and 10.8 of the pristine Cu-BTC at 273 K and 100 kPa, which also exceeds most reported adsorbents. Grand Canonical Monte Carlo (GCMC) simulations further elucidated that extra interaction with CO2 and 'sieve effect' for N2 or CH4 after FeTPPs encapsulation immediately boost CO2 uptakes and separation performance of FeTPPs@Cu-BTC. This study provides a new design idea for the development of new adsorbent materials.