Triphenylamine promoted geometric structure adjusting of the novel macrocyclic structure D-π-A conjugated microporous polymers for photocatalytic hydrogen evolution

Conjugated microporous polymers (CMPs) with a donor–acceptor (D-A) molecular structure usually express the properties of well light-induced electron/hole separation efficacy and high photocatalytic activity. The triphenylamine (TPA) with a special three-dimensional propeller structure was chose as the electron donor, and the dibenzothiophene sulfone (BTDO) groups as the chain scaffold and electron acceptor to construct and prepare a unique "macrocyclic structure" D-A type CMPs photocatalyst (TPA-BTDO) for photocatalytic hydrogen production (PHP). In order to further improve the conjugation degree of the CMPs and enhance the electron transfer capacity and light absorption, the thiophene units was introduced as "π-bridge" to form a macrocyclic D-π-A type CMPs photocatalyst (TPA-T-BTDO). The results show that the addition of thiophene greatly improves the coplanarity between the donor–acceptor units, and the prepared TPA-T-BTDO-1 exhibited an amazing PHP efficiency of 65.41 mmol h−1 g−1 in the visible light region. More importantly, the PHP efficiency also reaches up to 39.63 mmol h−1 g−1 under the natural light conditions. Both the characterizations and DFT simulation results prove that the twisted structure of the TPA donor decreases the dihedral angle between the benzene rings of BTDO and TPA, which improves the coplanarity of polymer skeleton and then prevents the charges transfer along the polymer chain for recombination. This study highlights the significant influence of the geometry of the electron donor on the photocatalytic activity, as well as the strategy of the structure adjusting by adding suitable bridges between the donor–acceptor units.