High-energy radiation that is compatible with renewable energy sources enables direct H 2 production from water for fuels; however, the challenge is to convert it as efficiently as possible, and the existing strategies have limited success. Herein, we report the use of Zr/Hf-based nanoscale UiO-66 metal− organic frameworks as highly effective and stable radiation sensitizers for purified and natural water splitting under γ-ray irradiation. Scavenging and pulse radiolysis experiments with Monte Carlo simulations show that the combination of 3D arrays of ultrasmall metal-oxo clusters and high porosity affords unprecedented effective scattering between secondary electrons and confined water, generating increased precursors of solvated electrons and excited states of water, which are the main species responsible for H 2 production enhancement. The use of a small quantity (<80 mmol/L) of UiO-66-Hf-OH can achieve a γ-rays-to-hydrogen conversion efficiency exceeding 10% that significantly outperforms Zr-/Hf-oxide nanoparticles and the existing radiolytic H 2 promoters. Our work highlights the feasibility and merit of MOF-assisted radiolytic water splitting and promises a competitive method for creating a green H 2 economy.

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The efficient use of renewable X/γ-rays or accelerated electrons for chemical transformation of CO2 and water to fuels holds promise for a carbon-neutral economy; however, such processes are challenging to implement and require the assistance of catalysts capable of sensitizing secondary electron scattering and providing active metal sites to bind intermediates. Here we show atomic Cu-Ni dual-metal sites embedded in a metal-organic framework enable efficient and selective CH3OH production (~98%) over multiple irradiated cycles. The usage of practical electron-beam irradiation (200 keV; 40 kGy min−1) with a cost-effective hydroxyl radical scavenger promotes CH3OH production rate to 0.27 mmol g−1 min−1. Moreover, time-resolved experiments with calculations reveal the direct generation of CO2•‒ radical anions via aqueous electrons attachment occurred on nanosecond timescale, and cascade hydrogenation steps. Our study highlights a radiolytic route to produce CH3OH with CO2 feedstock and introduces a desirable atomic structure to improve performance.

The role of the short-lived hydrated electron (e aq − ) has recently begun to be appreciated in per-and polyfluoroalkyl substances (PFAS) remediations; nevertheless, few studies to date focused on short-chain PFAS, and their effective defluorination has been limited by an insufficient mechanistic understanding, which starts with the elusive initial step of e aq − reduction. Herein, this study uses pulse radiolysis to clarify the rate constant of the e aq − reaction with a highly recalcitrant short-chain PFAS, perfluorobutanesulfonate (PFBS, C 4 F 9 SO 3 − ), and verify chain length dependence. The measured values contradict earlier results from laser photolysis but reconcile with the apparent degradation profiles and theoretical predictions. Besides, we first disclose radiolytic carbon dioxide radicals (CO 2 −• ) to defluorinate PFBS with an initial reaction constant of 4.8 × 10 7 M −1 s −1 , and it achieves selective cleavage on the more obstinate C−F bond than e aq − even under a neutral condition. Quantitative 60 Co γ-ray irradiation experiments further show that initial reduction occurs through a defluorination pathway rather than a desulfurization pathway, and the redox potential of PFBS exceeds −2.0 eV. This radiolytic study addressed the long-standing mechanistic contradictions regarding short-chain PFAS degradation and suggested ionizing radiation as a versatile and direct treatment technique.