Sustainable mixed-linker engineering of bio-derived Zr-metal–organic frameworks for tunable adsorption energetics and enhanced CO₂ uptake and selectivity

Mixed-linker engineering was used to enhance the adsorption performance of bio-derived Zr-based metal–organic frameworks (MOFs) through a completely green, scalable aqueous synthesis process. The gradual addition of fumaric acid into the MIP-202(Zr) framework enabled milder synthesis conditions, reducing the reaction temperature from 120 °C for pure MIP-202 to room temperature for fumaric-acid-rich compositions, without losing crystallinity. Nitrogen sorption analysis revealed a significant increase in surface area and microporosity with increasing fumaric acid content, improving the accessibility of adsorption sites. As a result, the mixed-linker frameworks exhibited much higher CO₂ uptake, with the 50–75% fumaric acid samples showing the best performance at both 273 K and 298 K. Isosteric heat and IAST analyses confirmed tunable CO₂–framework interactions and a notable improvement in CO₂/N₂ selectivity under post-combustion conditions. Additionally, the optimized MIP-202 (75% F.A.) sample showed promising performance in direct air capture (DAC) conditions, confirming its potential for CO₂ capture from ultra-dilute sources streams. Overall, this study demonstrates that green mixed-linker engineering is an effective approach to modify porosity and adsorption energetics in bio-derived Zr-MOFs for efficient low-pressure CO₂ capture.