Dependence of Dye Molecules Adsorption Behaviors on Pore Characteristics of Mesostructured MOFs Fabricated by Surfactant Template

Abstract

In this work, mesostructured metal−organic frameworks (MOFs) of MIL-101-Crs with different specific surface areas were synthesized successfully under solvothermal conditions using cationic surfactant cetyltrimethyl ammonium bromide (CTAB) as a structural template. It was found that crystallinity degrees, specific surface areas, and pore size distributions strongly depended on the loading of CTAB. Nitrogen adsorption and positron annihilation lifetime spectroscopy (PALS) results showed that the mean mesopore size increased with loading more CTAB due to the formation of larger templated mesopores. Although Langmuir adsorption of both methylene blue (MB) and methyl orange (MO) was confirmed in MIL-101-Crs, the experimental results showed different adsorption behaviors for them depending on the dye molecular size, pore structure, and charge properties of dye molecules/MOFs in solution. The MB molecules were found to be mainly adsorbed in the interspaces between grains and the templated mesopores, whereas the MO molecules were adsorbed in the inherent pores as well as the templated ones in MOFs due to the unsaturated metal sites' electrostatic attraction on them. Remarkably, MO adsorption capacity was observed to be proportional to the specific surface area, which allowed one to get a good linear fitting of experimental data. Interestingly, the good consistence between the fitting experimental parameter, that is, the number of adsorbed MO − s per unit specific surface area, and the calculated one according to our rough estimation strongly suggests that MO − s are electrostatically attracted and rotating around the unsaturated metal sites on MOFs' inner surfaces, which exclude other MO − s to be adsorbed around due to the "hindering effect" of the rotating motion.

Template-Assisted, Seed-Mediated Synthesis of Hierarchically Mesoporous Core–Shell UiO-66: Enhancing Adsorption Capacity and Catalytic Activity through Iterative Growth

“…Among the strategies that have been applied to the synthesis of HM MOFs, ,, templating with surfactants ,, has the potential to be the most general as it can be applied to a broad range of MOFs simply by combining a mesopore-forming template with the inorganic precursors and the organic linkers under a known MOF synthesis condition. In this manner, hierarchically porous HKUST-1, − MOF-5, MIL-101, , MIL-125, ZIF-8, , MIL-53­(Al), − and UiO-66 , have been achieved. However, undesirable impurities ,, and small crystalline domains often accompanied such template introduction, requiring extra efforts to fine-tune the synthetic condition or to purify and isolate the desired products.…”

Zn‐Vacancy Engineered S‐Scheme ZnCdS/ZnS Photocatalyst for Highly Efficient Photocatalytic H2 Evolution

“…Figure 5 shows the N 2 adsorption/desorption isotherm curves for the samples of MOF-5, ZnCdS and ZnCdS/ZnS(20) samples. In Figure 5a, based on IUPAC classification, the representative N 2 adsorption/desorption isotherm of MOF-5 is the type I (Langmuir isotherm), [42] the isotherms of ZnCdS and ZnCdS/ZnS both are type IV with H 3 hysteresis loops (Figure 5b-c), indicating that the ZnCdS and ZnCdS/ZnS samples have slit-like mesoporous properties and the pore structure is not very regular. [43] The BET surface area of MOF-5, ZnCdS and ZnCdS/ZnS samples are 654, 6 and 7 m 2 • g À 1 , respectively, Pore volume of MOF-5, ZnCdS and ZnCdS/ZnS(20) are 46.01, 0.01 and 6.62 cm 3 • g À 1 (Table 2), respectively.…”

Triggering Lewis Acidic Nature through the Variation of Coordination Environment of Cd-Centers in 2D-Coordination Polymers

“…Color as a property has perpetually fascinated humankind, for both aesthetic and social incentives throughout history. Nowadays, dyes emerge as a boost for large scale industries including in fibers, textiles, paper, plastics, chemicals, printing ink, leather, pharmaceuticals, cosmetics, acids, and foodstuff materials. − Out of all the dyes produced across the world, a massive percentage emanates as effluents from manufacturing and coloring processes. At present, textile industries are using approximately more than 10000 dyes out of which almost 70% is influenced with synthetic azo group dyes .…”