Donor-Acceptor Polymer Networks from Triarylborane and Thiophene Building Blocks for Photocatalytic Hydrogen Evolution from Aqueous Solution

Photocatalytic water-splitting provides a carbon-neutral alternative to energy-intensive electrolysis to store solar energy in the form of hydrogen. Microporous polymer networks are an intriguing platform for the design of increasingly more performant photocatalysts due to their chemical modularity and band-gap tuning potential. Their efficacy depends on the efficient separation of photoexcited electron-hole pairs. Conventionally, this is achieved by deposition of expensive platinum as co-catalyst. More recently, however, it was recognized that efficiency of polymer photocatalysts can be improved by incorporation of donor-acceptor motifs into their backbones. While electron donors are plentiful, there is little variety in electron acceptor motifs. We synthesised a series of microporous donor-acceptor networks that contain electron-deficient triarylborane moieties with the unique electronic properties of tricoordinate boron as an electron acceptor. Under sacrificial conditions, these polymers feature hydrogen evolution rates of up to 113.9 mmol h-1 g-1 that decrease only marginally under omission of platinum co-catalyst. This work outlines a clear synthetic strategy towards truly noble-metal-free photocatalysts.