Metal-ligand coordinated Schiff-base based conjugated microporous polymers as efficient electrocatalysts for oxygen evolution reactions

Creating efficient active oxygen evolution catalysts (OECs) from inexpensive, abundant elements is critical, as the inherently slow kinetics of the oxygen evolution reaction (OER) remain a major bottleneck limiting the efficiency of many electrochemical energy conversion technologies. We present a straightforward approach for synthesizing a novel BPhTz-Bz conjugated microporous polymers (CMPs) through an ionothermal [3+3] Schiff-base condensation between 1,3,5-tris(3′-tert-butyl-4′-hydroxy-5′-formylphenyl)benzene (Bz-3CHO) and 4′,4‴,4‴″-(1,3,5-triazine-2,4,6-triyl)tris(([1,1′-biphenyl]-4-amine) (BPhTz-3NH 2 ). Subsequently, the pristine BPhTz-Bz CMP was readily converted into a series of metal-coordinated materials, denoted as BPhTz-Bz-M CMPs (M 2+ = Co 2+ , Ni 2+ , Cu 2+ ), prepared by a simple metal ion incorporation of BPhTz-Bz CMP using the corresponding metal acetates. Both BPhTz-Bz CMP and BPhTz-Bz-M CMPs exhibited excellent thermal stability, with char yields reaching up to 60 wt% at 800 o C. Nitrogen adsorption–desorption (BET) analysis revealed that the original BPhTz-Bz CMP possesses a high specific surface area of 583 m 2 g -1 . After metal ion incorporation, the surface area decreased to 377, 355, and 392 m 2 g -1 for the Co-, Ni-, and Cu-containing CMPs, respectively. Electrochemical measurements demonstrated that the metal-coordinated CMPs exhibit significantly improved catalytic activity toward the OER in 1 M KOH. Among them, the BPhTz-Bz-Co CMP and BPhTz-Bz-Ni CMP showed the best performance, showing high catalytic performance with a 540 and 396 mV overpotential at 10 mA cm -2 , accompanied by a Tafel slopes of 123.3 and 71.4 mV dec -1 , and a turnover frequency (TOF) of 0.032 and 0.115 s -1 at an overpotential of 420 mV. These findings demonstrate that the combination of rational ligand design and transition-metal coordination yields a synergistic effect, enhancing electrocatalytic OER efficiency.