Construction of Metal-Coordinated Bipyridine-Based Conjugated Microporous Polymers as Robust Electrocatalysts for Hydrogen Evolution

Employing water splitting (WS) to develop electrocatalysts for the hydrogen evolution reaction (HER) presents a promising strategy for generating cost-effective energy. In recent years, extensive research has focused on designing metal-based conjugated microporous polymers (CMPs) catalysts with abundant electrocatalytically active sites, offering an efficient substitute for precious metal-based Pt/C catalysts. In this study, a series of microporous pyrene-metal CMPs (Ru, Fe, Co, and Ni) were synthesized via a one-pot Schiff-base [4 + 2] condensation reaction between 4,4’,4’’,4’’’-(pyrene-1,3,6,8-tetrayltetrakis(ethyne-2,1-diyl))tetraaniline [PyBZ-TB-4NH₂] and [2,2’-bipyridine]-5,5′-dicarbaldehyde [BPy-2CHO] in the presence of different derivatives of transition metal salts (Ru, Fe, Co, Ni) to afford PyBZ-TB-BPy-M CMPs. The uncoordinated PyBZ-TB-BPy CMP and coordinated PyBZ-TB-BPy-M CMPs were investigated for their electrochemical HER performance. Notably, PyBZ-TB-BPy-Ru CMP exhibited an impressively minimal overpotential of 285 mV (at 10 mA cm^–2) and a charge transfer resistance (R_ct) of 245 Ω at 280 mV overpotential in 1 M KOH electrolyte. Furthermore, PyBZ-TB-BPy-Ru CMP demonstrated excellent stability, maintaining its electrocatalytic activity with minimal performance degradation after 18 h of chronoamperometry. Additionally, PyBZ-TB-BPy-Fe, PyBZ-TB-BPy-Co, and PyBZ-TB-BPy-Ni CMPs displayed enhanced electrocatalytic activity compared to the PyBZ-TB-BPy CMP. The exceptional performance of these metal-coordinated PyBZ-TB-BPy-M CMPs highlights their potential as cost-effective, low-resistance electrocatalysts with highly exposed active sites for efficient alkaline HER.