Polytriphenylamine Conjugated Microporous Polymers and Polymer of Intrinsic Microporosity Composites as Platforms for Hydrogen Storage

Abstract

Hydrogen (H₂) is a promising clean energy carrier, but its practical storage remains a major challenge due to its low density, high-pressure or cryogenic requirements, and associated safety concerns. This thesis investigates the development and application of conjugated microporous polymers (CMPs) and CMP-based composites for enhanced H₂ storage performance. Chapter 1 begins with a comprehensive review of CMP synthesis strategies, characterisation methods, and structure–property relationships, providing a critical reference for researchers in the field. In Chapter 2, a suite of experimental techniques is described in detail, encompassing spectroscopic, microscopic, thermal, mechanical, and gas sorption analyses, with an emphasis on methodologies relevant to materials-based H₂ storage characterisation. In Chapter 3, polytriphenylamine (PTPA)-based CMPs were synthesised and optimised, achieving high specific surface areas (>1150 m² g⁻¹), micropore volumes (0.47 cm³ g⁻¹), and excess gravimetric H₂ capacities up to 2.51 wt % at 50 bar and 77 K. To enhance mechanical processability, composite membranes were fabricated using a polymer of intrinsic microporosity (PIM), specifically PIM-1, as the matrix and a PTPA-based CMP as the filler, as described in Chapter 4. The resulting composites achieved excess H₂ adsorption capacities of 1.03 wt % at 1 bar and 1.84 wt % at 50 bar, significantly outperforming pristine PIM-1 membranes, which reached only 0.87 wt % and 1.64 wt % under the same conditions. The composites also demonstrated faster H₂ uptake kinetics, with mass transfer coefficients of 3.42 min⁻¹ compared with 2.69 min⁻¹ for the PIM-1 matrix. Net adsorption isotherms further indicated advantages over conventional compressed gas storage at low pressures. The findings establish CMPs and their composites as promising candidates for next-generation solid-state H₂ storage systems. The thesis concludes in Chapter 5 with a discussion of limitations and future directions in tailoring CMP architectures and composite formulations for scalable, processable, capable H₂ storage applications.

Date of Award	20 Jan 2026
Original language	English
Awarding Institution	University of Bristol
Supervisor	Charl F J Faul (Supervisor) & Valeska Ting (Supervisor)