Functionalized Olefin-Linked Covalent Organic Frameworks for Selective Mercury Capture and Recovery from Vinyl Chloride-Rich Gas Streams

The calcium carbide-derived acetylene hydrochlorination route for vinyl chloride monomer (VCM, C2H3Cl) production remains a major source of mercury consumption and emission owing to its reliance on HgCl2/activated carbon catalysts. Selective removal of elemental mercury (Hg0) from crude VCM streams is intrinsically challenging because Hg0 must be captured from C2H3Cl-rich and HCl-containing atmospheres without coadsorbing valuable C2H3Cl. Here, we report a pore-engineered covalent organic framework (COF) platform in which olefin-linked sp2-carbon-conjugated frameworks suppress nonspecific C2H3Cl adsorption, while Cu-coordinated 2-(methylthio)ethoxy side chains create well-defined Cu-O2S2 pockets for selective Hg0 capture. These structural features afford an ideal adsorbed solution theory-predicted Hg0/C2H3Cl selectivity exceeding 20,000. Notably, dynamic breakthrough experiments under simulated industrial conditions containing 5 vol % HCl further revealed a Hg0 breakthrough time of over 10,000 min g-1 in C2H3Cl-rich streams, with a separation factor of approximately 52, demonstrating exceptional resistance to acid-induced deactivation. Treatment of the spent adsorbent with Na2S solution enables regeneration over 30 consecutive cycles and converts captured mercury into chemically stable HgS. This work establishes a molecularly precise removal-recovery platform for elemental mercury from chemically complex industrial gas streams, highlighting the power of programmed pore microenvironments to discriminate trace toxic species from abundant value-added molecules under chemically aggressive conditions.