Moderately Flexible Copper–Triazolate Framework with Quinone-Based Linkers: Balancing Effective CO2 Capture and Low-Energy Regeneration

Abstract

The development of advanced physisorption-based adsorbents is essential for carbon dioxide (CO2) capture technologies. While metal–organic frameworks (MOFs) offer a promising alternative to traditional carbon capture methods, they often face a trade-off between high adsorption affinity and energy-intensive regeneration. In this work, we report an anionic copper–triazolate framework, NCKU-56 (NCKU = National Cheng Kung University), incorporating quinone-based organic linkers. The 1D channels exhibit moderate structural flexibility and reversible lattice adjustments that are specifically correlated with CO2 adsorption. This material demonstrates high CO2/N2 IAST selectivity of 65 and 315 (50/50, 15/85, v/v) at 298 K and a moderate isosteric heat of adsorption of 30.1 kJ mol–1, which facilitates rapid regeneration without high thermal energy penalties. Crystallographic analysis reveals that the selective uptake is driven by cooperative host–guest interactions, including quadrupole−π interactions (with quinone cores and triazolate rings) and hydrogen bonding between CO2 and [NH2(CH3)2]+ cations. Breakthrough experiments confirm the practical efficacy of NCKU-56 for CO2/N2 separation, highlighting the potential of integrating polar functional groups and π systems with moderate framework flexibility for energy-efficient carbon capture.