Defects in a Metal-Organic Framework Fabricated by Carboxy-Functionalized Ionic Liquids for Enhancing NH3 Uptake

Ammonia (NH3) is a promising clean energy because of its high hydrogen density and carbon-free nature. Therefore, the capture, storage, and desorption of NH3 have received widespread attention in recent years. However, achieving highly efficient capture and release of NH3 remains a challenge. Herein, an efficient strategy is proposed to fabricate defects in a metal-organic framework (UiO-66) by using ionic liquid as a modulator for the first time. It is found that the NH3 adsorption capacity of the optimal defective UiO-66 is up to 1.60 times that of the pristine UiO-66 because of 16.8% of the linker missing. It is noteworthy that the adsorption of NH3 in the defective UiO-66 is completely reversible under conventional pressure-swing conditions, and more than 95% of the NH3 uptake capacity can be maintained after 30 adsorption-desorption cycles. It is revealed that the enhanced coordinating interaction of NH3 to Zr4+ and hydrogen bonding interactions between NH3 and oxygen-containing groups in the framework are the main driving forces for the substantially increased NH3 uptake. In addition, the strategy developed here is green and simple for manufacturing defects, which opens up a new pathway to the preparation of a wide range of solid adsorbents and catalysts.