Synergistic Transition-Metal Coordination within Pyrene- and Phenanthroline-Tethered Conjugated Microporous Polymers for Boosting Hydrogen Evolution Reaction in Alkaline Media

Abstract

Hydrogen (H2) production via electrochemical water (H2O) splitting relies heavily on the development of cost-effective and durable electrocatalysts to replace scarce and expensive platinum. Herein, we disclose a rationally conceived and executed synthesis of a pyrene (Py)- and phenanthroline (PhN)- tethered conjugated microporous polymer (CMP), where 1,10-phenanthroline (PhN) ligands (PyBz-PhN CMP) are incorporated through a C–Br/C–B Suzuki–Miyaura cross-coupling strategy. To enhance electrocatalytic activity, transition-metal ions (Fe2+, Co2+, Ni2+, and Ru2+) were coordinated with the PhN sites, affording a series of PyBz-PhN-M CMPs. Comprehensive characterization techniques, including Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), and scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM-EDS), confirmed successful metal coordination, excellent structural stability, and uniform metal dispersion throughout the framework. Among these catalysts, PyBz-PhN-Ru CMP exhibited the best HER performance, achieving overpotentials of 217 mV at 10 mA cm–2 in alkaline media and 180 mV in acidic conditions, alongside a reduced charge-transfer resistance (Rct) of 89 Ω. Combined density functional theory (DFT) calculations and experimental results reveal that modulation of the d-band center and reduced charge-transfer barriers are key to the enhanced catalytic activity. This study demonstrates that phenanthroline-functionalized CMPs serve as versatile and tunable porous platforms for incorporating transition metals, offering a practical approach to creating efficient and low-cost HER catalysts for clean H2 production.