Synthesis and Modification of Formate Zr-MOF (ZrFA) Toward Scalable and Cost-Cutting Gas Separation.

The mass production of metal-organic frameworks (MOFs) with affordable cost is highly demanding yet limited for commercial applications, e.g., purification of polymer-grade ethylene (C2H4) via acetylene (C2H2) and carbon dioxide (CO2) removal faces the challenge of developing low-cost and large-scale physisorbents with efficiency and recyclability. Herein, we developed a viable synthetic protocol to scale-up a series of ultramicroporous Zr-MOFs (ZrFA/ZrFA-D/ZrFA-D-Cu(I)) with the simplest monocarboxylate, formate (FA), through consecutive production by recycling solvent/modulator. Besides a size-exclusion effect disfavoring C2H4 adsorption, introduction of defective and Cu(I) sites was found to enhance gas affinity and uptake capacity. A comprehensive evaluation of C2H4 separation and economic efficiency has been proposed, suggesting the improvement of C2H2 uptake capacity is effective for the binary C2H2/C2H4 separation, while the separation process of the ternary C2H2/CO2/C2H4 mixtures depends on subtle tradeoff of complex factors and limited by challenging CO2/C2H4 separating. Notably, the large-scale separation has been testified to significantly improve separation efficiency, and the low-cost preparation benefits high economic efficiency. The distinct C2H2/C2H4/CO2 adsorption mechanism in ZrFA/ZrFA-D/ZrFA-D-Cu(I) has been elucidated by the theoretical calculations. This work may shed a light on the future C2H4 purification technology by pushing MOF-syntheses toward low-cost, scale-up, and recyclable production.