Synthesis of Hierarchically Structured Metal−Organic Frameworks by a Dual‐Functional Surfactant

Abstract

Hierarchically structured metal−organic frameworks (H−MOFs) are of great importance because of their widespread applicability in gas storage, separation, and catalysis. However, the synthesis of H−MOFs with tunable porosity and high stability is still a tremendous challenge. Herein, two strategies are developed to prepare classical porous MOFs—hierarchically structured HKUST−1 (H‐HKUST−1): (1) through utilizing a dual‐functional surfactant as a template individually, H‐HKUST−1 was successfully synthesized in a solvothermal system. The obtained H‐HKUST−1 products possess well‐ordered mesopores together with high thermal stability, the porosity of H‐HKUST−1 depends on the amount of the template and the type of extraction solvents. The multi‐ammonium head of the introduced surfactant bonded with BTC3− anion to form the main framework while the long alkyl chain filled the space to form mesopores. (2) H‐HKUST−1 was also prepared rapidly at room temperature and ambient pressure through the simultaneous addition of a dual‐functional surfactant and zinc oxide (ZnO). The synthesis time was only 1 min, with a space–time yield (STY) for the as‐synthesized H‐HKUST−1 as high as 3.1 × 104 kg⋅m−3⋅d−1, which is at least one order of magnitude higher than previously reported results. The present approach opens up new avenues for the templated synthesis of stable H−MOFs with tunable porosity and high stability for a wide range of applications.

Novel Hierarchical Fe(III)-Doped Cu-MOFs With Enhanced Adsorption of Benzene Vapor

“…However, Fe-HK-4 (Fe 3+ /Cu 2+ = 0.5) shows lower BET surface area than HKUST-1, which is possibly attributed to the formation of the serious crystal defects owing to the excess Fe 3+ (Zhou et al, 2016). After comprehensive consideration, Fe-HK-2 (Fe 3+ /Cu 2+ = 0.20) was chosen as the optimal sample, which presents BET surface area of 1,707 m 2 /g and total pore volume of 0.93 cm 3 /g, higher than the previously reported values for hierarchical-pore HKUST-1 prepared with different methods (Mao et al, 2015; Duan et al, 2018b,c).…”

“…These micropores can offer strong adsorption affinity toward VOCs molecules, but limit their diffusion rate, especially for large ones. Recently, Duan et al prepared hierarchical-pore HKUST-1 by employing organic amines or dual-functional surfactant as template and investigated its catalytic activity (Duan et al, 2018b,c). Nevertheless, the hierarchical-pore HKUST-1 exhibited lower BET surface area (584–1,241 m 2 /g) compared to the parent HKUST-1(1,425 m 2 /g).…”

Defective hierarchical porous copper-based metal-organic frameworks synthesised via facile acid etching strategy

“…26,33 Numerous methods to synthesise these types of hierarchical porous MOFs have been developed, including template-assisted routes (e.g. dual surfactant templating methods 27,34 and CO2-ionic liquid interfacial templating routes 35 ), template-free routes (e.g. facile self-assembly processes 36 and use of CO2-expanded solvents 23,37 ), spontaneous formation (via linker labilization 38 and metal-ligand fragmentation [39][40][41] ) and post-treatment (acid etching 42,43 and emulsion templating 44 ).…”

Water-based routes for synthesis of metal-organic frameworks: A review

“…Furthermore, based on similarity-intermiscibility theory, many organic ligands are hardly soluble in water [194]. In addition, MOF synthesis is largely conducted in solvothermal or hydrothermal conditions, which usually requires a high temperature and pressure with long reaction time, as indicated by the examples above [195,196]. These severe reaction conditions are also known to consume a lot of energy and reduce the production rate (in general STYs are below 300 kg m −3 per day) [55,197,198].…”