Scalable integration of MOFs, COFs, and MXenes with g-C3N4 for solar H2 generation: A review of energy conversion strategies

Abstract

Motivated by the transformative potential of photocatalytic water splitting for hydrogen (H₂) production, researchers are placing greater focus on this approach due to the increasing demand for sustainable and clean energy alternatives. As a corollary, recent strides in coupling metal-organic frameworks (MOFs), covalent organic frameworks (COFs), and MXenes with graphitic carbon nitride (g-C₃N₄) for solar-induced H₂ generation have been brought to light in this review. MOFs, with their tunable structures and high surface areas, enhance charge separation and interfacial transport, making them ideal for constructing efficient heterojunctions with g-C₃N₄. COFs, featuring light elements and modular synthesis, contribute extended light absorption and abundant catalytic sites, synergizing effectively with g-C₃N₄ to achieve superior H₂ evolution rates. Additionally, MXenes, exemplified by Ti₃C₂, introduce exceptional conductivity and broaden the absorption spectrum of g–C₃N₄–based heterojunctions, reinforcing their role in photocatalysis. Besides, this work critically examines the structural, electronic, and catalytic properties of these hybrid materials, emphasizing their impact on photocatalytic performance. The synthesis strategies for MOF/g-C₃N₄, COF/g-C₃N₄, and Ti₃C₂/g-C₃N₄ heterostructures are thoroughly reviewed, highlighting chemical compatibility and heterojunction engineering. Key approaches include precise fabrication techniques such as thermal, chemical, and physical etching for MXenes preparation and interfacial optimization for MOF and COF heterojunctions. Additionally, the recyclability and stability of these heterostructures are evaluated to assess their potential for sustainable H₂ generation. Benchmark results and scaling-up strategies are discussed to provide a comprehensive roadmap for achieving solar H₂ generation at practical scales. By integrating fundamental insights with cutting-edge developments, this review aims to guide future research in designing hybrid photocatalysts for a scalable and efficient H₂ economy.