Ethylenediamine-entrapped defective UiO-66(Zr) frameworks for improved CO2 adsorption and selectivity

In this work, ethylenediamine was entrapped to defected UiO-66(Zr) frameworks to harvest defective amine@UiO-66(Zr) adsorbent (ED@DUiO) that showed improved CO2 performance and good renewability owing to a synergetic effect of creating defects and introducing amine molecules. The UiO-66(Zr) framework was in-situ modified using an acetic acid modulator, followed by grafting of ethylenediamine into the defected UiO-66 (Zr) in n-hexane media. Results indicated that the defected UiO-66(Zr) framework had enhanced porosity and exposed more coordinatively unsaturated sites of Zr4+, favouring grafting amine molecules. Gas adsorption experiments revealed that ED@UiO exhibited significantly enhanced CO2 performance compared to the pristine MOF. At 25 degrees C and 100 kPa, the optimized ED@DUiO entrapped with -38.3 wt% amines exhibited a CO2- absorbing amount of -3.48 mmol/g, and IAST-CO2/CO and CO2/N2 selectivity of -46 and -78, respectively. Furthermore, the defected UiO-66 entrapped with ethylenediamine exhibited good separation of CO2 in the mixture with CO or N2 under dynamic flow adsorption conditions. The study provides a new strategy combining engineering defects and grafting alkylamine within MOF, which is a promising strategy for developing CO2-se-lective adsorbent materials.

Automated summary

In this study, ethylenediamine was encapsulated into defective UiO-66(Zr) frameworks to create an improved CO2 adsorbent. The results showed that the defective UiO-66(Zr) framework had increased porosity and exposed unsaturated sites, facilitating the grafting of ethylenediamine. Gas adsorption experiments revealed that the ethylenediamine encapsulated UiO exhibited significantly enhanced CO2 performance compared to the pristine MOF.