Enhanced Adsorption and Mass Transfer of Hierarchically Porous Zr-MOF Nanoarchitectures toward Toxic Chemical Removal

Abstract

Zirconium-based metal−organic frameworks (Zr-MOFs) have shown tremendous prospects as highly efficient adsorbents against toxic chemicals under ambient conditions. Here, we report for the f irst time the enhanced toxic chemical adsorption and mass transfer properties of hierarchically porous Zr-MOF nanoarchitectures. A general and scalable sol−gel-based strategy combined with facile ambient pressure drying (APD) was utilized to construct MOF-808, MOF-808-NH 2 , and UiO-66-NH 2 xerogel monoliths, denoted as G808, G808-NH 2 , and G66-NH 2 , respectively. The resulting Zr-MOF xerogels demonstrated 3D porous networks assembled by nanocrystal aggregates, with substantially higher mesoporosities than the precipitate analogues. Microbreakthrough tests on powders and tube breakthrough experiments on engineered granules were conducted at different relative humidities to comprehensively evaluate the NO 2 adsorption capabilities. The Zr-MOF xerogels showed considerably better NO 2 removal abilities than the precipitates, whether intrinsically or under simulated respirator canister/protection filter environment conditions. Multiple physicochemical characterizations were conducted to illuminate the NO 2 filtration mechanisms. Analysis on adsorption kinetics and mass transfer patterns in Zr-MOF xerogels was further performed to visualize the underlying structure−activity relationship using the gravimetric uptake and zero length column methods with cyclohexane and acetaldehyde as probes. The results revealed that the synergy of hierarchical porosities and nanosized crystals could effectively expedite the intracrystalline diffusion for the G66-NH 2 xerogel as well as alleviate the surface resistance for the G808-NH 2 xerogel, which led to accelerated overall adsorption uptake and thus enhanced performance toward toxic chemical removal.

“Ship-in-a-bottle” entrapment of biomolecules in MOF-based xerogel monoliths for high-performance electrochemical hydrogen evolution

“…32 Many MOFs in their gelbased form have been synthesized, for example, Zr-based MOFs (Universitetet i Oslo (UiO)-66 and 67, MOF-808, and Northwestern University (NU)-1000), 34 zeolitic imidazolate frameworks (ZIF)-8, 35 Hong Kong University of Science and Technology (HKUST)-1, 36 and Materials Institute Lavoisier (MIL)-100. 37 Due to the emergence of mesopores, xerogel monoliths are promising for gas adsorption, 12,36,38 removal of toxic contaminants, [39][40][41] and sensing. 42 Despite the fast-paced development, methods for controlling xerogel monolith mesopores have not been thoroughly investigated.…”

Continuously Tunable MOFs Enable Precise Mass Transfer for High-Performance Isomer Separation

“…Mass transfer is a fundamental process that widely exists in various fields, such as chemical engineering, environmental science, and biotechnology analysis. , Usually, mass transfer speed can significantly influence the rate of chemical and physical processes and finally affect the development of these areas. − The low mass transfer limits the access and departure of substances from the material active sites, leading to low application performances. − Thus, accelerating mass transfer has been recognized as an efficient way to obtain materials with high performance, high production throughput, and low energy cost. − However, the overfast mass transfer speed sometimes means insufficient contact between the substances and materials, resulting in incomplete reactions and separations . Meanwhile, the excessively fast mass transfer can also create steep concentration gradients that limit the diffusion of substances, leading to decreased efficiency .…”

Humidity Enhances the Solid-Phase Catalytic Ability of a Bulk MOF-808 Metal–Organic Gel toward a Chemical Warfare Agent Simulant

“…Metal–organic gels (MOGs), in particular, have come to prominent attention due to their adjustable hierarchical pore regimes and increased adsorption and catalysis capabilities. , Monolithic or granular MOGs can be obtained through tuning key reactions and post-treatment parameters. − The formation mechanism of these bulk architectures may be attributed to a colloidal network of discrete nanoparticles of crystalline MOFs that aggregate via noncovalent interactions . Granular MOGs may obviate practical application problems originating from MOF powders, and their hierarchically porous structures are conducive to accelerating the mass transfer rate and enhancing performance in adsorption and catalysis.…”

“…Metal−organic gels (MOGs), in particular, have come to prominent attention due to their adjustable hierarchical pore regimes and increased adsorption and catalysis capabilities. 17,18 Monolithic or granular MOGs can be obtained through tuning key reactions and post-treatment parameters. 19−23 The formation mechanism of these bulk architectures may be attributed to a colloidal network of discrete nanoparticles of crystalline MOFs that aggregate via noncovalent interactions.…”