Comprehensive Insights into the Synergistic Electrocatalytic Effects of Hierarchical Metal–Organic Framework Composites for Hydrogen Evolution Reaction

Pristine metal-organic frameworks (MOFs) possess inherently complex porous architecture with exceptionally high surface area and tunable porosity, making them ideal hosts for a broad spectrum of functional materials such as metals, metal oxides, carbon-based structures, and polymers. The structural engineering and synergistic integration have led to the emergence of hierarchical MOF-based composites with multiscale organization, establishing a niche for non-precious-metal systems that combine affordability, scalability, and catalytic performance on par with conventional platinum group metal-based hydrogen evolution reaction (HER) catalysts. This review comprehensively examines diverse pristine MOF-based composites engineered for HER, with an emphasis on how the incorporation of metallic and carbonaceous guest species effectively mitigates the inherent conductivity limitations and stability challenges of bare MOFs. The heterointerfaces created between the MOF matrix and the guest components play a decisive role in dictating porosity, surface morphology, and charge transfer properties. The correlation between the induced electronic coupling, band structure modulation, and enhanced electrocatalytic performance is critically analyzed. Furthermore, emerging design strategies and prospective research directions toward next-generation MOF-based electrocatalysts with improved durability and reaction efficiency are explored. Given the rapid progress in the hydrogen energy sector, this review aims to serve as a critical resource for the rational design of pristine MOF-based electrocatalysts, promoting innovation toward affordable and sustainable hydrogen production.