Intermingled Coordination Environments Enable Defect‐Engineered Metal–Polyphenol/G‐Quadruplex Hydrogel for Enhanced N2‐to‐NH3 Photoconversion

Why It Matters

It offers a low‑energy, scalable route to nitrogen fixation, reducing dependence on energy‑intensive Haber‑Bosch processes, and demonstrates how soft supramolecular assemblies can dramatically enhance photocatalytic performance.

Key Takeaways

• Bi3+‑caffeic acid embedded in G‑quadruplex hydrogel.
• Intermixed metal‑catechol/phosphate creates oxygen‑vacancy defects.
• Ion‑channel‑like pathways enhance charge and N2 diffusion.
• Visible‑light NH3 production reaches 905.2 µmol h⁻¹ g⁻¹.
• Performance 3.8× higher than non‑confined catalyst.

Pulse Analysis

Nitrogen fixation remains a cornerstone of modern agriculture, yet the conventional Haber‑Bosch method consumes roughly 1‑2 % of global energy output and emits substantial CO₂. Photocatalytic nitrogen reduction under ambient conditions promises a greener alternative, but achieving high activity and selectivity has been hampered by limited charge separation and poor substrate diffusion. Recent advances in defect engineering—introducing vacancies or heterojunctions at catalytic sites—have shown that tailoring electronic structures can unlock new reaction pathways, positioning defect‑rich materials at the forefront of sustainable catalysis research.

In this study, a Bi³⁺‑caffeic acid complex is immobilized within a GMP‑based G‑quadruplex hydrogel, creating a dual‑coordination environment that intertwines metal‑catechol and metal‑phosphate bonds. The resulting oxygen‑vacancy‑rich heterojunctions break local symmetry, facilitating rapid electron–hole separation. Simultaneously, the fibrillar hydrogel scaffold forms ion‑channel‑like conduits that streamline charge transport and provide unobstructed channels for N₂ molecules. This synergistic design yields a visible‑light‑driven ammonia synthesis rate of 905.2 µmol h⁻¹ g⁻¹, a 3.8‑fold improvement over the unconfined catalyst, highlighting the power of soft‑matter confinement in photocatalytic systems.

Beyond nitrogen fixation, the demonstrated strategy offers a template for integrating defect engineering with biomimetic matrices across a range of photochemical applications, from CO₂ reduction to organic synthesis. The hydrogel’s tunable composition and mild synthesis conditions suggest scalability and compatibility with existing manufacturing pipelines. As industries seek carbon‑neutral processes, such supramolecular platforms could accelerate the transition to decentralized, renewable‑driven chemical production, reinforcing the broader shift toward sustainable, low‑energy manufacturing.