Sulfur- and boron-containing porous donor-acceptor polymers for photocatalytic hydrogen evolution

Abstract

Photocatalytic water-splitting provides a way to store solar energy as hydrogen gas, and hence, is an attractive alternative to energy-intensive electrolysis of water. Microporous polymer networks are an interesting class of heterogeneous photocatalysts due to the chemical modularity of their optically active backbone and their guest-accessible pore-structure. Photocatalytic action depends on efficient separation of photoexcited electron-hole pairs, and recently, it was discovered that this separation can be improved by incorporation of donor-acceptor motifs into the polymer backbones. While there are many examples of electron donors, there is little variety in electron acceptor motifs. Here, we present a series of microporous donor-acceptor networks that contain electron-deficient boron moieties (triarylborane) as the electron acceptors and sulfur moieties (thiophene) as the donors. Under sacrificial conditions, these sulfur- and boron-containing polymers (SBPs) show rates of hydrogen evolution up to 113.9 mmol h-1 g-1. Conventionally used platinum co-catalyst does not contribute meaningfully to the photocatalytic action. Instead, palladium that is incorporated during the stage of polymer synthesis acts as the co-catalyst.