Direct waste-to-MOF synthesis: Scalable CO2-selective frameworks from zinc ash

Metal–organic frameworks (MOFs) are among the most promising materials for carbon dioxide capture, yet their large-scale deployment is limited by the cost and environmental footprint of conventional syntheses. Here, we demonstrate a direct and sustainable route to zinc-based MOFs by upcycling industrial zinc ash, a waste by-product of the steel galvanising industry, as the sole metal precursor. Using simple, room-temperature procedures in aqueous and alcoholic media, ZIF-7, ZIF-8, ZIF-11 and CALF-20 were synthesised directly from unpurified zinc ash with high yields and minimal processing. Comprehensive structural, compositional and morphological characterisation confirms that the resulting zinc-ash-derived MOFs retain the crystallinity, porosity and thermal stability of their counterparts produced from laboratory-grade reagents. Importantly, these materials exhibit comparable, and in some cases enhanced, CO 2 adsorption performance, including preservation of the gate-opening behaviour of ZIF-7 and high cyclic stability under binary CO 2 /N 2 conditions. This work illustrates the viability of industrial metal waste as a sustainable feedstock for advanced porous materials, offering a scalable pathway toward lower-cost and lower-impact MOF production for gas-separation applications .