A tube-like Pd@coordination polymer with enhanced solar light harvesting for boosting photocatalytic H2 production in a wide pH range and seawater

Abstract

Coordination polymers (CPs) have emerged as promising candidates for photocatalytic H₂ production owing to their structural tailorability and functional diversity. However, the development of CPs with high energy transfer efficiency for highly efficient photocatalytic H₂ production in a wide pH range still faces many challenges. Here we constructed a novel tube-like Pd(II) coordination polymer with well-distributed Pd nanoparticles (denoted as Pd/Pd(II)CPs) based on the coordination assembly of rhodamine 6G and Pd(II) ions and further photo-reduction under visible light irradiation. Both the Br⁻ ion and double solvent play a key role in forming the hollow superstructures. The resulting tube-like Pd/Pd(II)CPs exhibit high stability in aqueous solution with the pH range from 3 to 14 due to the high Gibbs free energies of protonation and deprotonation, which provides the feasibility of photocatalytic hydrogen generation in a wide pH range. Electromagnetic field calculations showed that the tube-like Pd/Pd(II)CPs have a good confinement effect on light. Therefore, the H₂ evolution rate could reach 112.3 mmol h⁻¹ g⁻¹ at pH 13 under visible light irradiation, which is far superior to those of reported coordination polymer-based photocatalysts. Moreover, such Pd/Pd(II)CPs could also reach a H₂ production rate of 37.8 mmol h⁻¹ g⁻¹ in seawater under visible light with low optical density (40 mW cm⁻²) close to morning or cloudy sunlight. The above unique characteristics make the Pd/Pd(II)CPs possess great potential for practical applications.