Singlet Oxygen (¹O₂)-Mediated Tunable Photocatalytic H₂O₂ Generation Using Donor-Acceptor Conjugated Microporous...

While generating hydrogen peroxide (H₂O₂) via a singlet oxygen (¹O₂) pathway is kinetically faster, it typically requires photocatalysts that exhibit efficient intersystem crossing (ISC). Herein, we report a series of donor-acceptor conjugated microporous polymers (CMPs), TPA-Btz, TPE-Btz, TPE-Ttz, and lpTPE-Btz, that produce H₂O₂ through the ¹O₂ pathway without relying on ISC or triplet energy transfer, instead driven by efficient interfacial electron transfer. By systematic variation of the donor, and acceptor components of the CMP network, the exciton properties are finely tuned, revealing the structure-property relationship of CMPs and their photocatalytic performance. While all the CMPs have sufficiently high conduction band potentials to reduce oxygen into superoxide anions (O₂^•-), in situ electron paramagnetic resonance (EPR) and scavenging studies revealed a significant contribution of the ¹O₂ pathway for H₂O₂ formation. Among the CMPs, TPA-Btz showed remarkably high H₂O₂ production rates of 3.8 mmol g^-1 h^-1 in pure water, with an apparent quantum yield of 8.71% and a solar-to-chemical-conversion (SCC) efficiency of 2.6%. Comprehensive computational analysis confirmed that the oxygen reduction reaction (ORR) pathway is thermodynamically favorable in all the CMPs, with a higher ΔG value for TPA-Btz, corroborating experimental observations. We have also demonstrated the generation of gram-scale quantities of solid-form H₂O₂ (Na₂CO₃·1.5H₂O₂), a step toward safer handling and transportation.