Selective adsorption of acetylene over carbon dioxide on glycine functionalized HKUST-1 with enhanced moisture stability

HKUST-1 is one of the most widely studied Metal-Organic Frameworks and is known for strong acetylene adsorption performance. However, it suffers from poor stability and lower working capacity after moisture exposure. To address this issue, we comparatively apply pristine HKUST-1 and glycine functionalized HKUST-1. They were prepared by a well-known low energy-consuming hydroxy double salt method. The ultrafast synthetic method was applied to obtain HKUST-1-ultrafast (HKUST-1-UF) and one glycine per three Cu sites was added HKUST-1 (HKUST-1-UF-GLY0.3). An adsorption study of C2H2 on the HKUST-1-UF and HKUST-1-UF-GLY0.3 shows that the introduction of glycine as the secondary binding unit increased the C2H2 uptake performance compared to that of bare HKUST-1. An evaluation of stability against moisture exhibits that the structural stability of HKUST-1-UF-GLY0.3 is enhanced compared to HKUST-1-UF. Further, in a breakthrough experiment using an equimolar C2H2/CO2 gas mixture, HKUST-1-UF-GLY0.3 exhibits a longer breakthrough time compared to HKUST-1-UF after thermal pre-treatment, or even pre-humidifying (RH 60% and RH 80%) overnight. The adsorbents can be repeatedly used as a C2H2 adsorbent over CO2.