Intrinsic Unsaturation and Azo-Functionality-Enriched Entangled MOF for Temperature-Responsive CO2 Selectivity with Atmospheric Pressure Size-Reliant Cycloaddition

The urgent need to mitigate rising atmospheric CO2 levels has amplified global interest in point-source capture and transformation of this greenhouse gas to value-added chemicals. Strategic modulation of the pore environment in metal–organic frameworks (MOFs) provides a versatile platform for high-temperature adsorption and efficient CO2 fixation. Herein, we report a robust and mixed-ligand-based Zn(II) framework, containing intrinsically unsaturated paddle-wheel metal nodes, azo (−NN−)-functionality, and π-electron-rich motifs, suitably arranged along the one-dimensional porous channels. This 3-fold interpenetrated MOF exhibits strong host–guest interactions and affords variable-temperature as well as humid conditions of CO2 adsorption while sustaining negligible loss across multiple uptake-release cycles. Notably, the CO2/N2 selectivity increases by 62.5% upon temperature increment from 273 to 313 K, surpassing many existing porous sorbents and highlighting its potential for practical gas separation. Advancing from synergistic participation of intrinsically unsaturated Zn(II) centers and Lewis-basic sites, the framework acts as a highly recyclable catalyst for solvent-free and atmospheric pressure CO2 fixation with epoxides, affording up to 98% conversion and >99% selectivity. The interpenetration-governed pore channel excludes sterically demanding epoxides and reveals the rarest size-selective cycloaddition reaction. Analyte-responsive emission modulation, together with inferior activity of a task-specific site-truncated iso-skeletal framework, clearly substantiates the synergistic participation of the Zn(II) center and azo functional moiety in catalysis. This study underscores the insightful design of hierarchical pore-size optimization and functionality engineering in an interpenetrated MOF to integrate high-temperature capture and energy-efficient chemical fixation of CO2 over a single platform.