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. 2024 Nov 13;12(1):nwae406.
doi: 10.1093/nsr/nwae406. eCollection 2025 Jan.

Tailoring rhodium-based metal-organic layers for parahydrogen-induced polarization: achieving 20% polarization of 1H in liquid phase

Jiawei Chen  1 , Qi Zhang  1 , Tao Chen  1 , Zeyu Zheng  1 , Yuhang Song  1 , Huichong Liu  1 , Ziqiao Chen  1 , Jing Wang  1   2 , Haoshang Wang  1 , Huijun Sun  1 , Xinchang Wang  1   3 , Zhong Chen  1   3 , Cheng Wang  1   3 , Zhongqun Tian  1   3
Affiliations

Tailoring rhodium-based metal-organic layers for parahydrogen-induced polarization: achieving 20% polarization of 1H in liquid phase

Jiawei Chen et al. Natl Sci Rev. .

Abstract

Heterogeneous catalysts for parahydrogen-induced polarization (HET-PHIP) would be useful for producing highly sensitive contrasting agents for magnetic resonance imaging (MRI) in the liquid phase, as they can be removed by simple filtration. Although homogeneous hydrogenation catalysts are highly efficient for PHIP, their sensitivity decreases when anchored on porous supports due to slow substrate diffusion to the active sites and rapid depolarization within the channels. To address this challenge, we explored 2D metal-organic layers (MOLs) as supports for active Rh complexes with diverse phosphine ligands and tunable hydrogenation activities, taking advantage of the accessible active sites and chemical adaptability of the MOLs. By adjusting the electronic properties of phosphines, TPP-MOL-Rh-dppb (TPP = tris(4-carboxylphenyl)phosphine), featuring a κ 2-connected di(phosphine) ligand, generated hyperpolarized styrene achieving an over-2400-fold signal enhancement and a polarization level of 20% for 1H in methanol-d 4 solution. The TPP-MOL-Rh-dppb effectively inherited the high efficiency and pairwise addition of its homogenous catalyst while maintaining the heterogeneity of MOLs. This work demonstrates the potential of 2D phosphine-functionalized MOLs as heterogeneous solid support for HET-PHIP.

Keywords: heterogeneous catalysts; hyperpolarization; metal-organic layers; nuclear magnetic resonance; parahydrogen-induced polarization.

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Figures

Figure 1.
Figure 1.
(a) Structure of the TPP-MOL. (b) Schematic representation of Rh complexes within MOLs, showing variations in the number and electronic structures of phosphine ligands for PHIP application.
Figure 2.
Figure 2.
(a) TEM, (b) HAADF and (c) AFM images of the TPP-MOL. The inset in (b) is the fast Fourier transform (FFT) pattern. (d) TEM, (e) HAADF and EDX mapping, and (f) AFM images of TPP-MOL-Rh-dppb. The insets in (c) and (f) depict the height profile along the white line (H represents height). (g) PXRD patterns of various TPP-MOL derivatives alongside the simulated pattern of the monolayer model. (h) 31P-NMR spectra of the digested MOL catalysts.
Figure 3.
Figure 3.
Structures and PASADENA 1H-NMR spectra of (a, b) TPP-MOL-Rh, (c, d) TPP-MOL-Rh-P, (e, f) TPP-MOL-2PPh3 and (g, h) TPP-MOL-Rh-dppb catalysts with Rh loading of 0.44 mol%. The spectra of the separated supernatant after the reaction are included (below), normalized to signals in the aromatic region and presented on the same vertical scale.
Figure 4.
Figure 4.
(a) Summary of normalized PASADENA 1H-NMR spectra using 33% p-H2. (b) Signal enhancement (SE) and (c) turnover frequency (TOF) of TPP-MOL-Rh, TPP-MOL-Rh-P, TPP-MOL-2PPh3 and TPP-MOL-Rh-dppb catalysts in phenylacetylene hydrogenation. The SE error bars in (b) were derived from multiple PASADENA experiments in Table S2. TOF was calculated based on the 1H-NMR data of normal H2 (n-H2) hydrogenation.
Figure 5.
Figure 5.
PASADENA 1H-NMR spectra using 96% p-H2 of TPP-MOL-Rh-dppb with Rh loading of (a) 0.44 mol%, (b) 0.30 mol% and (c) 0.11 mol%, respectively, normalized to signals in the aromatic region and presented on the same vertical scale. The spectra using n-H2 are included (below, vertically scaled by 10-fold). (d) Comparison of SE factor and proton polarization.
Figure 6.
Figure 6.
The normal H2 and D2 hydrogenation of (a) TPP-MOL-Rh-dppb catalyst and (b) Rh(COD) (dppb)BF4 catalyst (to account for the drift of deuterium chemical shifts, O2NPhCOOCD3 with its known chemical shift at ∼4 ppm was added for calibration).
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References

    1. Pravdivtsev AN, Buntkowsky G, Duckett SB et al. Parahydrogen-induced polarization of amino acids. Angew Chem Int Ed 2021; 60: 23496–507.10.1002/anie.202100109 - DOI - PMC - PubMed
    1. Wang W, Wang Q, Xu J et al. Understanding heterogeneous catalytic hydrogenation by parahydrogen-induced polarization NMR spectroscopy. ACS Catal 2023; 13: 3501–19.10.1021/acscatal.2c05659 - DOI
    1. Bouchard LS, Burt SR, Anwar MS et al. NMR imaging of catalytic hydrogenation in microreactors with the use of para-hydrogen. Science 2008; 319: 442–5.10.1126/science.1151787 - DOI - PubMed
    1. Rossini AJ, Zagdoun A, Lelli M et al. Dynamic nuclear polarization surface enhanced NMR spectroscopy. Acc Chem Res 2013; 46: 1942–51.10.1021/ar300322x - DOI - PubMed
    1. Pokochueva EV, Burueva DB, Salnikov OG et al. Heterogeneous catalysis and parahydrogen-induced polarization. ChemPhysChem 2021; 22: 1421–40.10.1002/cphc.202100153 - DOI - PubMed

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