Construction of Stable Metal−Organic Frameworks by Integrating Phosphonic Groups into Building Blocks

Abstract A novel metal‐organic framework (MOF), constructed by Cu 2+ and 4‐phosphonobenzoic acid (H 3 pbc), namely SL‐1, was prepared via solvothermal synthesis in a mixture of H 2 O and N,N‐dimethylacetamide (DMA). The crystalline structure of SL‐1 was revealed by single crystal X‐ray diffraction (SC‐XRD) analysis, which demonstrates the existence of two different coordination geometries of cooper nodes. Cu1 center is anchored by two carboxylate groups from two H 3 pbc ligand and coordinates with three water molecules, while Cu2 center is six‐coordinated that results in ‐CuO 6 ‐CuO 6 ‐CuO 6 ‐CuO 6 ‐ double helix structure. Remarkably, the robust SL‐1 demonstrates excellent acid and base resistance when soaking in aqueous solution with pH value ranging from 4–12. In addition, after a high temperature process (~100 °C), the water molecules linked by carboxylate anchored Cu node would be released, while the crystalline nature was preserved and almost unchanged. As a result, the exposed and unsaturated Lewis acid active sites can effectively catalyze aerobic oxidation of benzyl alcohol to benzaldehyde with yield of 73 % and selectivity of nearly 100 %. We believe the presented strategy by integrating phosphonic groups into building blocks to afford stable MOF structure will guide the design of more practical functionalized MOF materials.