Multiple-Site Engineered Metal-Organic Frameworks for Efficient One-Step Separation of Methanol-to-Olefin Products...

Efficient one-step adsorption separation of light hydrocarbons (LHs) from methanol-to-olefin products and natural gas is highly desirable in the petrochemical industry. However, designing adsorbents that simultaneously achieve high selectivity and capacity remains a critical challenge. Here, we report a microporous Zn-based metal-organic framework (MAC-4-F) decorated with electronegative O, N, and F trifunctional sites, which markedly enhance host-guest interactions for the selective recognition of multi-C-H-bond gases such as C₃H₆ and C₃H₈. The well-defined pore environment (∼4.2 Å) and high surface area (1295.8 m²·g^-1) endow MAC-4-F with outstanding adsorption capacities of 5.0 and 4.7 mmol·g^-1 for C₃H₆ and C₃H₈, respectively, at 298 K and 100 kPa, together with high IAST selectivity values of 9.8 (C₃H₆/C₂H₄), 15.4 (C₂H₆/CH₄), and 91.6 (C₃H₈/CH₄). Dynamic breakthrough-desorption experiments further confirm its ability to produce high-purity C₂H₄ (46.9 L·kg^-1) and enrich C₃H₆ (13.3 L·kg^-1) in a single step, as well as recover high-purity CH₄ (349.5 L·kg^-1) and C₃H₈ (18.6 L·kg^-1) from light alkane mixtures. Moreover, MAC-4-F exhibits excellent moisture stability and recyclability. Theoretical calculations reveal that the N-O-F sites reinforce multiple interactions (C-H···F/O/N, C···O-H, and C-H···π) with target molecules. Overall, this work demonstrates MAC-4-F as a highly competitive dual-function adsorbent for olefin or alkane separation from LHs, while providing new insights into the design of MOFs with electronegative-rich functional sites to overcome the capacity-selectivity trade-off in LH separation.