Pillared MOFs: structure and ring opening polymerization of cyclic esters

Gong, Yi; Cheng, Fei; Chen, Fei; Beamish-Cook, Jethro; Elsegood, Mark R.J.; Elsegood, Mark Robert James; Derbyshire, Max; Rowe, Oliver; Redshaw, Carl

Abstract

The solvothermal reaction of Zn(NO3)2·6H2O with 5-aminoisophthalic acid and 4,4′-bipyridyl (4,4′-bipy) led to the self-assembly of the known 3-D hybrid H-bonded/covalent structure {[Zn(5-AIP)(4,4′-bipy)0.5]·DMF}n (1·DMF), but with DMF here (rather than H2O as previously): an analogous reaction using the related 4,4′-azopyridine (4,4′-azopy) in place of 4,4′-bipyridyl afforded the structurally related framework {[Zn(5-AIP)(4,4′-azopy)0.5]·0.75DMF}n (2·0.75DMF). Similar solvothermal reactions of Co(NO3)·6H2O, Mn(NO3)·4H2O and Cd(NO3)·4H2O with 5-aminoisophthalate and the potential linkers 4,4′-bipy, 2-di(4-pyridyl)ethylene (DPE), and 4,4′-azopy afforded the porous 3-D structures {[Co2(NO3)2(5-AIP)(4,4′-bipy)2]·2EtOH}n (3·2EtOH), {[Co(5-AIP)(DPE)]·2DMF}n (4·2DMF), {[Co(5-AIP)(4,4′-azopy)]·2DMA}n (5·2DMA), {[Mn(5-AIP)(4,4′-bipy)]·2DMA}n (6·2DMA), {[Mn(5-AIP)(DPE)]·6DMF}n (7·6DMF), {[Mn(5-AIP)(4,4′-azopy)]·2.5DMF}n (8·2.5DMF), the previously reported {[Cd(5-AIP)(4,4′-bipy)]·3DMF}n (9·3DMF), {[Cd(5-AIP)(DPE)]·DMF}n (10), and {Cd(5-AIP)(4,4′-azopy)(DMF)}n (11), with structures 4-10 bearing the same network topologies with metal atoms and 5-AIP ligands in sheets, bipy ligands acting as pillars, and solvent molecules of crystallisation located around the bipy ligands. The activated MOFs were employed as catalysts for the ring opening polymerization (ROP) of ϵ-caprolactone and δ-valerolactone. ROPs were conducted as melts, and under N2 only 1 with δ-VL (∼93% conversion) was active. In the case of ϵ-CL under air, all the systems were active with 1, 2, and 11 affording >90% conversion. Molecular weights (Mn) were in the range 3760-17 940 Da and the products formed were identified as both cyclic and linear PCL. For δ-VL, the catalysts performed somewhat better, with all systems (except 8) affording ∼90% conversion or more under air. Molecular weights (Mn) were in the range 2180-7940 and as for PCL, the products formed were identified as both cyclic and linear PCL.

Citation

Gong, Y., Cheng, F., Chen, F., Beamish-Cook, J., Elsegood, M. R., Elsegood, M. R. J., …Redshaw, C. (2023). Pillared MOFs: structure and ring opening polymerization of cyclic esters. CrystEngComm, 25(2), 267-283. https://doi.org/10.1039/d2ce01317g

• Journal Article Type: Article
• Acceptance Date: Nov 24, 2022
• Online Publication Date: Nov 25, 2022
• Publication Date: Jan 14, 2023
• Deposit Date: Nov 25, 2022
• Publicly Available Date: Jan 3, 2023
• Journal: CrystEngComm
• Electronic ISSN: 1466-8033
• Publisher: Royal Society of Chemistry
• Peer Reviewed: Peer Reviewed
• Volume: 25
• Issue: 2
• Pages: 267-283
• DOI: https://doi.org/10.1039/d2ce01317g
• Keywords: Condensed Matter Physics; General Materials Science; General Chemistry
• Public URL: https://hull-repository.worktribe.com/output/4132461