Formation and fine-tuning of metal-organic frameworks with carboxylic pincers for the recognition of a C 2 H 2 tetramer and highly selective separation of C 2 H 2 /C 2 H 4 .

Highly efficient ethylene (C 2 H 4 ) and acetylene (C 2 H 2 ) separation is a great challenge and an important process in current industries. Herein, we finely tune a new family of 6-c metal-organic frameworks (MOFs) with crab-like carboxylic pincers for the recognition of a C 2 H 2 tetramer and afford NTU-72 with high adsorption C 2 H 2 /C 2 H 4 selectivity (56-441, 298 K) as well as unprecedented recovery of both highly pure C 2 H 4 (99.95%) and C 2 H 2 (99.36%). Furthermore, the effective binding of a C 2 H 2 tetramer by NTU-72's carboxylic pincers has been revealed by gas-loaded crystallography and Raman spectral studies. Our work provides a novel approach for the selective binding of a small molecular cluster for designing high-performance MOFs.