# Alkaline-adaptive covalent organic framework photocatalysts: synergistic molecular orbital and hydrogen-bond network engineering for H2O2 production

## TL;DR

This paper introduces a new covalent organic framework that efficiently produces hydrogen peroxide in alkaline conditions by improving charge dynamics and hydrogen bonding.

## Contribution

The study introduces a dual-engineering strategy combining molecular orbital and hydrogen-bond network design for enhanced alkaline H2O2 production.

## Key findings

- TP-PZ-COF achieved a 4961 µmol g−1 h−1 H2O2 production rate in 0.01 M NaOH, an 8.1-fold improvement over TP-AN-COF.
- Phenazine units in TP-PZ-COF enhance OH− affinity and interfacial enrichment, accelerating 4e− WOR kinetics.
- The generated H2O2 effectively degraded industrial dye pollutants.

## Abstract

Alkaline hydrogen peroxide (H2O2) is highly desirable for critical applications due to its superior stability and reactivity, but it is incompatible with conventional near-neutral production methods. While covalent organic frameworks (COFs) show promise for photocatalytic H2O2 generation, their alkaline performance is severely limited by poor charge dynamics and inadequate hydrophilicity, hindering the essential 2e− oxygen reduction reaction (ORR: O2 + 2e− + H2O → HO2− + OH−) and 4e− water oxidation reaction (WOR: 4OH− → O2 + 2H2O + 4e−). This work pioneers a dual-engineering strategy (molecular orbital and interfacial hydrogen-bonding network engineering) within β-ketoenamine-linked COFs to overcome these challenges simultaneously. By contrasting phenazine-based (TP-PZ-COF) and anthracene-based (TP-AN-COF) COFs, we demonstrate that strategic integration of sp2-N heteroatoms modulates molecular orbitals and enhances n → π* transitions, optimizing charge separation and transport for efficient 2e− ORR and 4e− WOR. Concurrently, the planar phenazine units form robust hydrogen-bonding networks that dramatically boost hydroxide ion (OH−) affinity and interfacial enrichment, thereby accelerating the 4e− WOR kinetics. This integrated approach enabled TP-PZ-COF to achieve an exceptional alkaline H2O2 production rate of 4961 µmol g−1 h−1 in 0.01 M NaOH, representing an 8.1-fold increase over TP-AN-COF (606 µmol g−1 h−1). The generated H2O2 efficiently degraded industrial dye pollutants. Direct experimental and theoretical validations confirmed the cooperative mechanism between charge dynamics optimization and OH− affinity enhancement, providing a new blueprint for designing on-demand alkaline H2O2 photocatalysts.

A phenazine-based COF was engineered via molecular-orbital modulation and hydrogen-bond network construction, improving charge separation/transfer and OH− adsorption for efficient alkaline H2O2 production via the cooperative 2e− ORR/4e− WOR.