Artificial photosynthesis of hydrogen peroxide (H 2 O 2 ) using sunlight, water and air offers a decentralized green alternative to energy‑intensive industrial anthraquinone manufacturing. However, slow kinetics of the four‑electron water‑oxidation reaction (WOR) severely restricts solar‑to‑chemical efficiency. Conventional covalent organic frameworks (COFs) mostly adopt imine linkages, which lack sufficient hydrogen‑bonding sites to facilitate proton transport, even though they exhibit good crystallinity and porosity.
Herein, the research team from Nankai University reported a linker‑editing strategy to construct ordered hydrophilic hydrogen‑bond networks inside urea‑COF pore channels. By tuning electronegativity of N/O/S atoms among imine‑, thiourea‑ and urea‑linkages, continuous proton transport pathways are formed. Theoretical simulations and multiple characterizations confirm that the hydrogen‑bond network acts as a proton highway via ultrafast Grotthuss‑type proton hopping and quantum‑assisted proton tunneling, lowering the activation barrier of rate‑limiting water‑oxidation reaction. Benefiting from the optimized pore microenvironment, the urea‑COF delivers an outstanding photocatalytic H 2 O 2 generation rate of 4104 μmol g −1 h −1 , which is 2.8 times the performance of imine‑COF. Its apparent quantum yield reaches 7.2 % at 405 nm. The catalyst retains over 90 % activity after six recycling cycles and works stably in tap water, river water and seawater under natural sunlight.
To bridge molecular‑level material design and practical application, the researchers immobilized urea‑COF into buoyant porous hydrogel beads to build a solid‑liquid‑gas tri‑phase reactor. The floating device can directly capture atmospheric oxygen and realize easy catalyst recovery. It enables in‑situ H 2 O 2 production for efficient Escherichia coli disinfection and degradation of diverse organic micro‑pollutants. Compared with powder‑form catalysts, the hydrogel‑bead system extends continuous‑operation durability by 2.8‑fold. Life‑cycle assessment and techno‑economic analysis demonstrate that the floating reactor cuts the levelized cost down to 14.6 USD per kilogram H 2 O 2 , showing great promise for decentralized on‑site water remediation.
This work highlights the significance of interfacial proton‑flux modulation for solar H 2 O 2 synthesis, and provides a feasible blueprint for translating porous‑catalyst lab achievements toward real‑world environmental applications.
Science Bulletin
Experimental study