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

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.