Selenium-Substitution Strategy for Enhanced Mobility, Tunable Bandgap, and Improved Electrochemical Energy Storage in Semiconducting Conjugated Coordination Polymers

Abstract

Conjugated coordination polymers (c-CPs), a novel class of organic–inorganic hybrid materials, are distinguished by their unique structural characteristics and exceptional charge transport properties. The electronic properties of these materials are critically determined by the constituting coordination atoms, with electron-rich selenol ligands emerging as promising candidates for constructing high-mobility semiconducting c-CPs. Despite their potential, c-CPs incorporating selenium-substituted ligands remain scarce due to the synthetic challenges associated with both the ligands and the coordination polymers. In this study, we successfully synthesized a new tetraselenol-hydroxyquinone (TSHQ) ligand using a “4+2” design strategy and developed a semiconducting three-dimensional Ag−Se coordination polymer, Ag₄TSHQ. Ag₄TSHQ exhibits room-temperature electrical conductivity of up to 1.6 S/m and shares the same structural topology as Ag₄TTHQ (TTHQ=tetrathiol-hydroxyquinone), enabling precise band gap modulation from 0.6 eV to 1.5 eV via a mixed-ligand approach. Time-resolved terahertz spectroscopy reveals that the charge mobility of Ag₄TSHQ in the dc limit is ~350 cm²/V ⋅ s, which is twice that of its sulfur counterpart, Ag₄TTHQ. Furthermore, our evaluations of their electrochemical energy storage capabilities demonstrate that Ag₄TSHQ effectively utilizes its redox potential, achieving a remarkable specific capacitance of up to 340 F/g-significantly outperforming Ag₄TTHQ, which has a capacitance of 294 F/g. These findings underscore the potential of selenium-ligand-based c-CPs for optoelectronic applications and energy storage technologies.