Covalent organic frameworks (COFs) have emerged as advanced materials for addressing heavy metal pollution in acidic environments. However, powdered COF adsorbents face challenges such as poor operability and a tendency to agglomerate, limiting their industrial wastewater treatment applications. In this study, we prepared a sulfur-rich COF-OSH/mPTFE composite membrane through in situ growth and subsequent modification of COFs on the surface of amino-functionalized PTFE porous membranes. The COF-OSH/mPTFE composite exhibits a remarkable adsorption capacity for mercuric cations (Hg2+), reaching 223.5 mg/g. Notably, even at pH 1, the adsorption capacity remains high at 68.9 mg/g. The adsorption process demonstrates excellent resistance to interference from Na+ and Ca2+ ions and shows good reusability. Furthermore, COF-OSH/mPTFE reduced the concentration of Hg2+ in a 100 mL solution (5 mg/L) by over 80 % within 13 min at pH 5, and by over 40 % at pH 2. Even after continuous treatment of 20 L of Hg2+ solution, a significant reduction in Hg2+ concentration in the filtrate was still observed. The COF-OSH/mPTFE composite membrane addresses the cleanliness and recovery issues associated with powdered adsorbents in adsorption environments. The simple, efficient, and low-energy filtration process endows COF-OSH/mPTFE with excellent capability for treating acidic wastewater containing Hg2+.