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

Jiawei Chen; Qi Zhang; Tao Chen; Zeyu Zheng; Yuhang Song; Huichong Liu; Ziqiao Chen; Jing Wang; Haoshang Wang; Huijun Sun; Xinchang Wang; Zhong Chen; Cheng Wang; Zhongqun Tian

doi:10.1093/nsr/nwae406

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

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

Authors

Jiawei Chen¹, Qi Zhang¹, Tao Chen¹, Zeyu Zheng¹, Yuhang Song¹, Huichong Liu¹, Ziqiao Chen¹, Jing Wang^{1

2}, Haoshang Wang¹, Huijun Sun¹, Xinchang Wang^{1

3}, Zhong Chen^{1

3}, Cheng Wang^{1

3}, Zhongqun Tian^{1

3}

Affiliations

¹ State Key Laboratory of Physical Chemistry of Solid Surfaces, School of Electronic Science and Engineering, Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China.
² College of Biology and Environmental Engineering, Zhejiang Shuren University, Hangzhou 310015, China.
³ Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (IKKEM), Xiamen 361005, China.

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.