Double-Anchored Triphenylamine-Fluorene Functionalized Dyes for High-Performance Photocatalytic Hydrogen Generation

Two novel metal-free organic dyes, namely the mono-anchoring KMT1 and di-anchoring KMT2 dyes, have been synthesized to function as photosensitizers for utilizing in photocatalytic hydrogen production systems. They adopt the donor-donor-π-acceptor and donor-donor-(−π-acceptor)₂ configurations, respectively, featuring triphenylamine and fluorene moieties as electron donors, thiophene as the π-bridges and cyanoacrylic acid as the acceptors/anchoring groups. It was found that the photocatalytic performance of the di-anchoring dye significantly outperforms that of its mono-anchoring counterpart. KMT2-based photocatalytic system demonstrated remarkable performance, producing 3520 μmol (84.9 mL) of hydrogen over a span of 257 hours under blue light irradiation, with a turnover number (TON) of 56300, a turnover frequency (TOF_i) of 1862.7 h⁻¹, an initial hydrogen production activity (activity_i) of 1164180 and an apparent quantum yield (AQY_i %) of 19.9. This performance is among the top-tier when compared to other dyes used in similar photocatalytic systems. The results clearly illustrate that the di-anchoring dye possesses several advantages, including a broad absorption spectrum, higher absorptivity, and a relatively slower charge recombination rate. These attributes collectively contribute to its superior overall performance in photocatalysis.