Temperature-Variant\nCO<sub>2</sub> Separation in Entangled\nMetal-Organic Framework with Carboxamide Functionality-Fueled Atmospheric-Pressure\nCycloaddition and Size-Exclusive Tandem Knoevenagel Condensation

The pressing need to lower atmospheric carbon dioxide\n(CO<sub>2</sub>) concentration has captivated global focus on point-source\ncapture\nand transformation of this greenhouse gas to chemicals. Purpose-driven\npore-functionality engineering in metal–organic frameworks\n(MOFs) can lead to high-temperature and humid-condition adsorption\nand efficient cycloaddition of CO<sub>2</sub> and further assist in\nachieving unconventional methodologies for sustainable tandem catalysis.\nHerein, we develop a [Zn<sub>2</sub>(COO)<sub>4</sub>N<sub>4</sub>] building unit-containing chemo-robust framework with carboxamide\nfunctionality, free oxygen atoms, and π-electron-rich moieties\naffixed to one-dimensional channels. This 3-fold entangled MOF exhibits\nstrong framework–gas interactions and unveils variable-temperature\nCO<sub>2</sub> adsorption with recurrent capture–release cycles\neven under 75% relative humidity. Interestingly, the CO<sub>2</sub>/N<sub>2</sub> selectivity shows a remarkable 82% increase with an\nincrease in the temperature from 273 K (79) to 313 K (143), which\noverpowers several porous adsorbents and validates potential of this\nMOF in flue gas separation. This microporous MOF catalyzes solvent-free\nand recyclable CO<sub>2</sub> cycloaddition with various epoxides\nunder atmospheric pressure. In contrast to the classical Lewis acid-mediated\nreaction, controlled experiments, including performance comparison\nof a urea functionality-truncated isostructural framework corroborate\nthe unique two-point hydrogen bonding-mediated cycloaddition pathway.\nThe suitably oriented carboxamide moiety within the MOF channels further\nacts as a hydrogen bond donor (HBD) site in the tandem deacetalization–Knoevenagel\ncondensation reaction with >99% conversion under solvent-less mild\nconditions in 4 h. The cooperative role of acid–base dual sites\nin substrate activation is comprehensively supported by studies using\nexternal additives, fluoro-titration-derived interactions, and comparison\nwith an unfunctionalized framework. To the best of our knowledge,\nin this one-pot reaction, acetals having larger molecular dimensions\nexhibit poor formation of α,β-unsaturated dicyanides,\nand demonstrate pore-fitting-mediated size-exclusive catalysis.