(i) they act as electron acceptors, and (ii) they improve the wettability of the aromatic polymer backbone. In this work, we integrate for the first time a readily available triarylborane-based electron acceptor into a donor-acceptor polymer photocatalyst. Tricoordinate boron features an intrinsic electron gap and an empty p-orbital on boron that enables charge-transfer interactions with adjacent aromatic substituents and gives rise to unique optical and electronic effects. For example, triarylboranes are used in organic light-emitting diodes and as selective chemical sensors for fluoride ions. Herein, we show that polymer networks based on sulfur-containing heterocyclic donors and triarylborane-based acceptors (SBPs) have a high efficiency as hydrogen evolution photocatalysts under visible-light and sacrificial conditions. The principal borane building block used herein is accessible via commercial brominated and iodinated 1,3-dimethylbenzene. Selective lithiation of the iodide at -78 °C followed by nucleophilic attack on boron trifluoride diethyl etherate yields tris(4-bromo-2,6dimethylphenyl)borane (TAB). The stannylated thiophene building blocks are either commercially available or synthetically accessible using a deprotonation-stannylation route. Following our reported procedure, 2 the Stille-type polymerization of C2-symmetric donor to C3-symmetric acceptor units in a 3:2 ratio affords powders of TT-TAB, BDT-TAB, and BT-TAB of vibrant yellow and orange colors (Scheme 1). We performed nitrogen sorption experiments at low-temperature, and calculated the accessible surface areas according to the Brunauer-Emmett-Teller (BET) model (Error! Reference source not found.C and Figure in the supporting information). The rigid polymer backbones of TT-TAB and BDT-TAB afford comparative large surface areas of 755 and 664 m 2 g -1 , respectively. BT-TAB contains bithiophene units linked by flexible, single bonds, and consequently, the material does not show significant, guest-accessible pores (BET of 66 m 2 g -1 ).