Defect-induced pore engineering in HKUST-1 by N-doped graphene quantum dots for CO₂ adsorption enhancement

Global climate change has been a serious issue, and the innovation of CO₂ reduction technologies has become a universal consensus and trend. The preparation of hierarchical porous metal-organic frameworks (MOFs) is an effective approach to improve CO₂ adsorption performance due to the accelerating the diffusion of gas flow and exposing more adsorptive pore surface. In this study, an innovative synthesis method that enlarges the pore size of HKUST-1 through utilizing nitrogen doped graphene quantum dots (NGQDs) was developed to induce defect formation during its self-assembly process. The mesoporous and total pore volume of HKUST-1@NGQDs-3 was 0.27 and 0.48 cm³/g, respectively, which was 58.8 % and 23.1 % higher than those of pure HKUST-1. The HKUST-1@NGQDs-3 exhibited high CO₂ adsorption capacity of 4.03 mmol/g at 1 bar, elevated up to 53.8 % compared to pristine HKUST-1 owing to its mesoporous structure. Importantly, the CO₂/N₂ selectivity was significantly improved up to 31.7 % at 1 bar compared to HKUST-1. Additionally, the isosteric heat of adsorption for HKUST-1@NGQDs was lower than that of pure HKUST-1, facilitating the regeneration of adsorbent. This work presents a simple and efficient strategy for the developing MOFs-based composites for enhanced CO₂ capture.