Sub-Minute Synthesis of Nano-Cofs as Highly Efficient Photocatalysts for Enhanced H2 Evolution in Seawater

Abstract

Developing efficient and scalable strategies for constructing photocatalysts, especially those compatible with seawater environments, is critical for advancing solar-to-hydrogen energy conversion. Covalent organic frameworks (COFs) have garnered increasing attention due to their tunable band structures, high surface areas, and exceptional chemical stability. However, conventional synthesis methods are often time-consuming and offer limited control over particle morphology, restricting their practical applicability. Herein, we present a droplet-based microfluidic approach for the sub-minute (~60 s), continuous, and scalable synthesis of nanoscale β-keto-enamine-linked COFs with uniform fibrous morphology (~50 nm). The optimized TpPa COF exhibits outstanding photocatalytic H₂ evolution activity under visible light, achieving hydrogen evolution rates of 342.20 mmol·g⁻¹·h⁻¹ in simulated seawater and 288.60 mmol·g⁻¹·h⁻¹ in real seawater, along with a high apparent quantum efficiency (AQE) of 8.60% at 420 nm. These performances exceed those of most reported COF-based photocatalysts and underscore the material’s excellent stability and seawater tolerance. Density functional theory (DFT) calculations further reveal how specific ion–COF interactions influence charge separation and transport, offering mechanistic insight into the differing catalytic behaviors in simulated versus real seawater. This work demonstrates a promising strategy for the rapid fabrication of seawater-compatible COF photocatalysts toward sustainable hydrogen production.

Keywords: Covalent organic frameworks (COFs), Droplet microfluidics, Sub-minute synthesis, photocatalytic hydrogen evolution, seawater splitting