Upcycling Spent Li-Ion Battery Waste into Benchmark Metal–Organic Frameworks for CO ₂ Capture under Flue-Gas Conditions

High Resolution Image Download MS PowerPoint Slide The rapid growth of the lithium-ion battery (LIB) market has generated large volumes of end-of-life cathode waste, particularly from NMC and LCO batteries, which are rich in Ni, Mn, and Co. Conventional recycling routes rely on strong-acid leaching and extensive conditioning, creating extreme pH conditions that prevent direct reuse in advanced materials synthesis. In this study, we demonstrate a scalable, non-acidic strategy that converts two end-of-life LIB streams (NMC electric-mobility packs and LCO phone batteries) into mixed-metal feeds, which are used as-is to synthesize four isoreticular mixed-metal Ni/Co- and Co/Mn-MOF-74 sorbents. A non-acid NH 4 Cl salt-roasting/water-leaching process affords clear mixed-metal leachates (S1 and S2) that directly yield IRMOF-74-I and IRMOF-74-II without pH adjustment when the two linkers, 2,5-dihydroxyterephthalic acid (H 4 dobdc) and 4,4′-dihydroxy-[1,1′-biphenyl]-3,3′-dicarboxylic acid (H 4 dobpdc), are used. PXRD/VT-PXRD, TGA, and N 2 sorption confirmed the formation of crystalline, thermally robust, microporous MOF-74 frameworks, while ICP-OES and SEM−EDS verified the homogeneous incorporation of mixed-metal Ni/Co or Co/Mn nodes. CO 2 adsorption measurements under post-combustion conditions demonstrate capture performance comparable to that of MOF-74 materials synthesized from commercial metal salts, achieving 5.40−7.11 mmol g −1 at 298 K and 1 bar, with Q st (0) = 31–40 kJ mol −1 . Under a fixed-bed breakthrough with a 15/85 v/v CO 2 /N 2 mixture at 298 K, dynamic capacities of 2.40−2.97 mmol g −1 are obtained, consistent with equilibrium uptakes at flue-gas partial pressures (2.67–3.50 mmol g −1 at 0.15 bar). Dynamic testing under a humidified feed (40% RH) shows a reduction in CO 2 capacity due to the competitive adsorption of H 2 O at open metal sites. Solvent reuse (DMF) preserves crystallinity while negligibly affecting N 2 textural properties and CO 2 uptake, thereby strengthening the sustainability and scale-up potential of this LIB-to-MOF platform for CO 2 separation.