Ethylenediamine-entrapped defective UiO-66(Zr) frameworks for improved CO2 adsorption and selectivity
Ngoc Chuc Pham, The Ky Vo, Quang Bac Nguyen, Kien Trung Nguyen, Thi Ha Chi Nguyen, Ngoc Nhiem Dao, Jinsoo Kim, Van Cuong Nguyen
Abstract
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 CO 2 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 Zr 4+ , favouring grafting amine molecules. Gas adsorption experiments revealed that ED@UiO exhibited significantly enhanced CO 2 performance compared to the pristine MOF. At 25 °C and 100 kPa , the optimized ED@DUiO entrapped with ∼ 38.3 wt% amines exhibited a CO 2 -absorbing amount of ∼ 3.48 mmol/g, and IAST-CO 2 /CO and CO 2 /N 2 selectivity of ∼ 46 and ∼ 78, respectively. Furthermore, the defected UiO-66 entrapped with ethylenediamine exhibited good separation of CO 2 in the mixture with CO or N 2 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 CO 2 -selective adsorbent materials.