Fluorescent Sulphur‐ and Nitrogen‐Containing Porous Polymers with Tuneable Donor–Acceptor Domains for Light‐Driven Hydrogen Evolution

Abstract

Light-driven water splitting is a potential source of abundant, clean energy, yet efficient charge-separation and size and position of the bandgap in heterogeneous photocatalysts are challenging to predict and design. Synthetic attempts to tune the bandgap of polymer photocatalysts classically rely on variations of the sizes of their π-conjugated domains. However, only donor-acceptor dyads hold the key to prevent undesired electron-hole recombination within the catalyst via efficient charge separation. Building on our previous success in incorporating electron-donating, sulphur-containing linkers and electron-withdrawing, triazine (C N ) units into porous polymers, we report the synthesis of six visible-light-active, triazine-based polymers with a high heteroatom-content of S and N that photocatalytically generate H from water: up to 915 μmol h g with Pt co-catalyst, and-as one of the highest to-date reported values -200 μmol h g without. The highly modular Sonogashira-Hagihara cross-coupling reaction we employ, enables a systematic study of mixed (S, N, C) and (N, C)-only polymer systems. Our results highlight that photocatalytic water-splitting does not only require an ideal optical bandgap of ≈2.2 eV, but that the choice of donor-acceptor motifs profoundly impacts charge-transfer and catalytic activity.

Reducing the Exciton Binding Energy of Donor–Acceptor‐Based Conjugated Polymers to Promote Charge‐Induced Reactions

“…For the spectra shown in Figure e, it is easily observed that these polymers have different PL lifetimes and the estimated average lifetimes ( τ avg ) increased in order of FSO‐FS z , FSO‐BP, FSO‐F, and FSO‐FS. This tendency is accordance with the decrease of E b , suggesting that the high charge mobility in these polymers is due to the lower energy loss of E CT .…”

Reducing the Exciton Binding Energy of Donor–Acceptor‐Based Conjugated Polymers to Promote Charge‐Induced Reactions

“…Figure S11 shows the room-temperature PL spectra of all of the polymers.A sE b decreases,acorresponding PL quenching is observed, indicating ad ecreased recombination of photogenerated charges. [19] Moreover, the time-resolved PL spectra show the lifetimes of the charges.For the spectra shown in Figure 2e,itis easily observed that these polymers have different PL lifetimes and the estimated average lifetimes (t avg ) increased in order of FSO-FS z ,F SO-BP,F SO-F,a nd FSO-FS.T his tendency is accordance with the decrease of E b ,s uggesting that the high charge mobility in these polymers [20] is due to the lower energy loss of E CT .…”

Exploring the “Goldilocks Zone” of Semiconducting Polymer Photocatalysts by Donor–Acceptor Interactions

“…Exchange of Pt co-catalyst to Pd can even diminish photocatalytic activity of conjugated porous polymers,a sitwas shown in our previous study. [25] In summary, we setout to examinerationaldesignconcepts fore nhancedp hotocatalystsb ased on theh ighly-modular family of sulfur andn itrogen containing porous polymers (SNPs).W edesignedeight SNPs ystems that featureasimilar pore structureyet have arange of opticalbandgapsand come with andw ithout spacersb etween thed onor (aromatic thiophenes)a nd acceptor (triazine) moietiest oe nables trong andw eakc harge-transfere ffects,r espectively. Composition, properties,a nd computationalr ationalization of thesep olymers narrowsd ownt he "GoldilocksZ one" fort he ideal polymerp hotocatalyst as follows: 1) Therei saconceivable rangeo fo ptimal (indirect) band gaps forp hotocatalysis between2 .1 and2 .3 eV that eclipses thep rotonr eduction andthe sacrificialdonor oxidationpotentials.…”