With the guidance of the hard/soft acid/base principle, we adopt a strategy to construct a novel robust metal−organic framework (MOF) by using a dual-functional ligand to coordinate with different types of metal ions in a onepot reaction through coordination self-selection. A bimetallic MOF, namely BUT-85 (BUT = Beijing University of Technology), has been successfully synthesized with a rationally designed pyrazolate-carboxylate ligand. Its robust [Ni 2 (OH)-(H 2 O) 2 Pz 3 ] n chain (Pz = pyrazolate) with bridging OH − /H 2 O and pyrazolate groups is reported for the first time. This material shows good chemical stability in water and aqueous solutions with a pH range from 3 to 13. In addition, BUT-85 exhibits preferential adsorption behavior of C 2 H 2 over CO 2 . It is proposed to be attributed to the abundant exposed bridging OH − /H 2 O sites in [Ni 2 (OH)(H 2 O) 2 Pz 3 ] n chains, which is supported by the results of molecular simulations. Column breakthrough experiments further confirm that this MOF can realize efficient C 2 H 2 / CO 2 separation. This strategy can not only enrich the structural library of MOFs but also optimize their properties and functions for promoting applications.

The development of ethane (C 2 H 6 )-selective adsorbents for ethylene (C 2 H 4 ) purification, although challenging, is of prime industrial importance. Pillared-layer metal-organic frameworks (MOFs) possess facilely tunable pore structure and functionality, which means they have excellent potential for high-performance C 2 H 6 /C 2 H 4 separation applications. Herein, we report a family of isostructural pillared-layer MOFs with various metal centers M and co-ligands L, M 2 (D-cam) 4 L 2 (denoted M-cam-L; M = Cu, Co, Ni; L = pyz, apyz, dabco), with a variety of pore surface properties. All of the M-cam-L materials exhibit preferential adsorption for C 2 H 6 over C 2 H 4 . In particular, Ni-cam-pyz exhibits the highest C 2 H 6 capture capacity (68.75 cm 3 g À1 at 1 bar and 298 K), Cu-cam-dabco possesses the greatest C 2 H 6 /C 2 H 4 adsorption selectivity (2.3), and the lowest isosteric heat of adsorption is demonstrated for Cu-cam-pyz (20.1 kJ mol À1 ).Dynamic column breakthrough experiments also confirmed the excellent separation performance of M-cam-pyz and M-cam-dabco materials. The synthesis route of the M-cam-L materials is easily scaled-up under laboratory conditions, and hence this class of MOFs is promising for practical C 2 H 4 purification.

The separation of acetylene (C 2 H 2 ) from carbon dioxide (CO 2 ) and methane (CH 4 ) is of great significance, but remains challenging, because of their similar physicochemical properties, and it currently has received substantial research interest by using adsorptive separation based on metal−organic frameworks (MOFs). Herein, a new microporous Cu-MOF, [Cu(5-OH-IPA 2− )-(DPYA)(H 2 O)] (BUT-318, where 5-OH-IPA 2− = 5-hydroxyisophthalate and DPYA = 4,4′-dipyridylamine) has been synthesized successfully under solvothermal conditions, which exhibits excellent separation performance for C 2 H 2 /CO 2 and C 2 H 2 /CH 4 gas mixtures. The presence of Cu(II) open metal sites and different Lewis base sites (−OH and −NH) make the activated BUT-318 efficiently bind C 2 H 2 and exhibit high adsorption capacity under low pressure (24.52 and 9.1 cm 3 g −1 under 0.01 bar, at 273 and 298 K, respectively). The corresponding IAST (ideal adsorbed solution theory) selectivity was 9.8 and 244.3 at 273 K and 1 bar for an equimolar C 2 H 2 /CO 2 and C 2 H 2 /CH 4 mixture. The separation performance and reusability under dynamic conditions were also confirmed by column breakthrough experiments, making BUT-318a a promising candidate for the practical C 2 H 2 separation.