Structural Exploration of Zirconium Metal-Organic Frameworks Through Linker Desymmetrization and Modulator Compensation.

Zirconium-based metal-organic frameworks (Zr-MOFs) feature exceptional thermal/chemical stability among various MOFs, enabling diverse applications. Their material properties are highly dependent on molecular structures consisting of Zr-clusters and organic linkers. However, structural diversity in Zr-MOFs remains constrained by the limited variety of known Zr-clusters and the predominance of high-symmetry linkers, which stems from the inherent symmetry constraints presented by Zr-clusters. In this work, we develop a linker-desymmetrization-modulator-compensation (LDMC) strategy to construct Zr-MOFs with enhanced structural diversity. This approach reduces linker symmetry to create structural defects in Zr-clusters, while such a thermodynamically unfavorable process can be compensated for by the coordination of modulators, such as benzoic acid and formic acid. As a result, two MOFs, PCN-1005 and PCN-1006, with unprecedented Zr-clusters have been constructed. PCN-1005 features an asymmetric Zr6 cluster stabilized by mono- and capping benzoates. In PCN-1006, a rare pentacarboxylate linker enables the formation of a dual-node network comprised of both Zr6 and Zr6-f-Zr6 clusters, resulting in one-dimensional channels with exceptional adsorption performance for methane and carbon dioxide, affording high selectivity over hydrogen. These findings underscore the advancement of the LDMC strategy in promoting the structural complexity and functionality of Zr-MOFs, providing a versatile platform for energy and environmental applications.