Ya-Nan Ma, Teng-Long Liu, Wei-Hong Zhang, Cheng-Hang He, and Dong-Xu Xue*. Angew. Chem. Int. Ed. 2025, ASAP. DOI: https://doi.org/10.1002/anie.202513208

The pursuit of advanced adsorbents with exceptional gas adsorption and separation capability represents a highly promising yet challenging research frontier. Several quinary multicomponent metal-organic frameworks (MOFs) have been documented in the literature, however, the construction of quinary MOFs through the synergistic integration of two distinct organic ligands and three different metal clusters remains scarce.

Herein, solvothermal reaction of Zn(OAc)₂·2H₂O with adenine and 1,2,4-benzenetricarboxylic anhydride afforded a novel MOF of Quin-Zn-Ad-BTC. SCXRD reveals that Quin-Zn-Ad-BTC incorporates three distinct zinc-based structural units of a mononuclear [ZnN₂(O₂C─)₂], a dinuclear [Zn₂(Ad)₃(O₂C─)₂], and a hexanuclear [Zn₆N₃(μ-H₂O)₃(Ad)₃(O₂C─)₆], respectively. It features three interconnected cage-like cavities replete with uncoordinated carboxylate oxygen atoms and Watson─Crick sites.

The MOF was successfully activated through multiple methanol exchanges followed by vacuum heating. It exhibits a pore volume exceeding 0.50 cm³ g^-1 and a gravimetric surface area surpassing 1220 m² g^-1. At 298 K and 1 bar, its adsorption capacities for C₂H₂ and C2H₆ consistently surpass that of C₂H₄. Quin-Zn-Ad-BTC demonstrates low isosteric heats of adsorption (Q_st) for all three gases, indicating excellent regenerability. Ideal Adsorbed Solution Theory (IAST) calculations reveal selectivity values of 2.05 for 50/50 C₂H₂/C₂H₄ and 1.26 for 10/90 C₂H₆/C₂H₄ mixtures. Breakthrough experiments further confirm its unique capability for one-step ethylene purification from ternary C₂ hydrocarbon mixtures. Additionally, C₂H₄ and C₃H₆ adsorption isotherms were measured at 298 K and 1 bar, complemented by Q_st analysis and IAST predictions. Simulated breakthrough experiments with methanol-to-olefins (MTO) products demonstrate the material’s potential for separating MTO effluent streams.

In this study, we have successfully synthesized a new quinary MOF of Quin-Zn-Ad-BTC through a one-pot solvothermal reaction. Due to its distinctive structural features, the material demonstrates outstanding ethylene purification capability, enabling highly efficient one-step ethylene separation from complex C₂ mixtures and MTO products under ambient pressure conditions. These findings not only validate the feasibility of quinary MOFs for advanced applications in gas adsorption and light hydrocarbon separation, but also establish a new paradigm for assembling complex multicomponent MOFs.

Figure 1. Schematic representation showing the assembly of Quin-Zn-Ad-BTC.

Figure 2. (a) C₂H₂, C₂H₄ and C₂H₆ sorption isotherms at 298 K for Quin-Zn-Ad-BTC. (b) Q_st of C₂H₂, C₂H₄, and C₂H₆ gases. (c) IAST selectivity for 10%/90% (v/v) of C₂H₆/C₂H₄ and 50%/50% (v/v) of C₂H₂/C₂H₄ mixtures. (d) Experimental column breakthrough curves for C₂H₂/C₂H₄ /C₂H₆ (1/1/1, v/v/v) mixtures under a flow of 1 mL min^-1.

Figure 3. (a) C₂H₄ and C₃H₆ sorption isotherms at 298 K for Quin-Zn-Ad-BTC. (b) Q_st of C₂H₄, and C₃H₆ gases. (c) IAST selectivity for (20%/50%, v/v) of C₃H₆/C₂H₄ mixtures. (d) Experimental column breakthrough curves for C₃H₆/C₂H₄/He (0.2/0.5/0.3, v/v/v) mixtures under a flow of 4 mL min^-1.

First Author: Ma Yanan, doctoral candidate, Shaanxi Normal University

Correspondence Author: Prof. Xue Dongxu, Shaanxi Normal University

Full Text Link: https://doi.org/10.1002/anie.202513208