In situ construction of hierarchical ultrasmall MOF aerogels with tunable mesopores for selective adsorption and efficient catalysis

Abstract

Metal–organic frameworks (MOFs) have garnered extensive research interest due to their ultrahigh porosity and flexible tunability. However, the predominantly microporous structures of most reported MOFs impose substantial mass transfer resistance and restrict the exposure of active sites, while their powdered form poses a major bottleneck for industrialization. In this work, hierarchical ultrasmall MOF aerogels with micro/mesoporous structures and a high specific surface area, HP-UiO-66-NH₂-X@WCA, are successfully synthesized via an in situ construction strategy driven by H₂O/Acetic acid (Ace) competitive nucleation. Notably, the fabricated HP-UiO-66-NH₂-X@WCA under this solvent-regulated environment effectively exposes more active sites and promotes the rapid diffusion of large molecules due to its ultrasmall nanoparticles (<25 nm) and tunable interconnected mesopores (3.7–21.3 nm). Moreover, HP-UiO-66-NH₂-X@WCA exhibits excellent structural stability and elasticity, imparting exceptional durability and convenient recyclability in practical applications. Benefiting from the above advantages, HP-UiO-66-NH₂-X@WCA demonstrates superior macromolecular selective adsorption and efficient catalytic activity compared to microporous MOF aerogels with larger particle sizes. Furthermore, when HP-UiO-66-NH₂-X@WCA is packed into a fixed-bed reactor for continuous-flow catalysis, it exhibits excellent activity and stability over long-term operation. This work offers new insights into the controlled design and fabrication of high-performance hierarchical MOF aerogels for practical adsorption and catalytic applications.