Orthogonalization of Polyaryl Linkers as a Route to More Porous Phosphonate Metal‐Organic Frameworks. Issue 31 (13th April 2022)

• Record Type: Journal Article
• Authors: Glavinović, Martin; Perras, Justin H.; Gelfand, Benjamin S.; Lin, Jian‐Bin; Shimizu, George K. H.
• Is Part Of: Chemistry. Volume 28:Issue 31(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-04-13
• Subjects: gas capture -- ligand design -- metal-organic frameworks -- phosphonates -- porous solids; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.202200874
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: The coordinative pliancy of the phosphonate functional group means that metal‐phosphonate materials often self‐assemble as well‐packed structures with minimal porosity, as efficient inter‐ligand packing is enabled. Here, we report a multistep synthesis of a novel aryl‐phosphonate linker with an orthogonalized ligand core, 1, 3, 5‐tris(4'‐phosphonophenyl)‐2, 4, 6‐trimethylbenzene (H6 L2) designed to form more open structures. A series of crystalline metal‐phosphonate frameworks (CALF‐35 to ‐39) have been assembled by coordinating to divalent metals (Ba, Sr, Ca, Mg, Zn). H6 L2 is unable to pack efficiently and, as a consequence, yields several distinct microporous structures. The resulting structures are discussed in detail, with a focus on the solid‐state packing of the sterically rigidified linker. Combined with larger cations (Sr, and Ba), H6 L2 packs in a parallel‐offset manner, yielding isomorphous and microporous metal‐organic frameworks (CALF‐35 (Sr), and (Ba)). When coordinated to smaller metals (Ca, Mg, Zn), H6 L2 forms four new structures. Two Ca MOFs of different stoichiometry, (CALF‐36 and 37) and a Mg MOF CALF‐38 show narrow pores and have high selectivities for CO2 over N2 and CH4 . Finally, in CALF‐39 (Zn), H6 L2 linkers pack in a herringbone fashion, resulting in a material with 10.9×10.1 Å 2 square channels. The stability of all structures was tested, and the most porous structure, CALF‐39 (Zn), was found to retain its structure and gas adsorption after immersion in water over pH 3–11. Abstract : Orthogonalization of components inhibits efficient packing, whether of bagels or polyaryl linkers in metal‐organic frameworks (MOFs). This strategy was applied to polyphosphonate linkers to generate six new MOF structures (CALF‐35 to ‐39). Ba, Sr, Mg, Zn and two Ca structures were obtained from a new trigonal linker with orthogonal peripheral aryl rings to inhibit efficient packing. The structures are discussed considering their porosity, stability and selective sorption of gases.