PubMedSmall methods2026-10-26
Symmetry-Breaking Polarized Ir-COFs With Ultralow Exciton Binding Energy Enable Directional Charge Allocation for Synergistic Photocatalytic Gold Recovery and BPA Photodegradation.
Chen Yi-Ru YR, Wang Xiu X, Wang Ruixiang R, Li YiBao Y et al.
Synergistic photocatalytic precious metal recovery and organic pollutant degradation promise sustainable resource recovery. However, this process is constrained by high exciton binding energy and disordered carrier migration, inducing charge crosstalk and sluggish kinetics among competing redox centers. A molecular induced polarization symmetry-breaking (MIP-SB) strategy constructs a polarized Ir-functionalized covalent organic framework (COF), BT-mBpyCN2+-Ir, where Ir coordination creates a π-d-π* coupled electronic structure promoting directional ligand-to-ligand charge transfer (LLCT) for efficient charge allocation. This structural design generates a built-in electric field, with Kelvin probe force microscopy (KPFM) showing a surface potential of 120 mV. This strong internal field yields an ultralow exciton binding energy of 24.7 meV and a prolonged carrier lifetime of 1.85 ns. This directional charge allocation enables a mutual promotion effect: the bisphenol A (BPA) degradation rate constant increases by 21-fold in the presence of Au(III), while the Au(III) reduction rate is enhanced by 3.8-fold when BPA co-exists. Consequently, under sacrificial-agent-free conditions, BT-mBpyCN2+-Ir achieves 99.4% BPA degradation within 30 min and a gold extraction capacity of 3145 mg g-1. Density functional theory (DFT) calculations confirm that BPA coexistence lowers the Gibbs free energy for Au(III)-to-Au(0) conversion, revealing a thermodynamically favored dual-channel synergistic mechanism.