Rational construction of defects in a metal–organic framework for highly efficient adsorption and separation of dyes

Effect of Benzoic Acid as a Modulator in the Structure of UiO-66: An Experimental and Computational Study

“…We speculate that this volatilization could occur to different extents and rates from one synthesis batch to the next, potentially affecting reproducibility -a situation which is completely avoided by using the non-volatile benzoic acid (B.P. = 249.2 °C) as the modulator; (3) In our experience, trifluoroacetic acid modulated UiO-66 syntheses often provide poor yields, a negative outcome is much less severe when benzoic acid is employed as the modulator; (4) trifluoroacetic acid modulated syntheses tend to yield UiO-66 samples with very poorly defined crystal morphology and size 37,50 , while benzoic acid modulated syntheses provide reasonably monodisperse octahedral crystals 20,49,59,77 ; (5) benzoic acid is much cheaper than trifluoroacetic acid.…”

“…In acknowledgement of this challenge, researchers have sought to develop methods that are able to detect, quantify, and evaluate the nature of the defects in different UiO-66 samples, preferably with routine characterization techniques available in most home labs. To this end, most research groups (including our own) employ some combination of PXRD 37,49,52,54,73 , TGA 37,49,50,[53][54][55]58,61,68,69,73 , dissolution/ 1 H NMR spectroscopy 37,47,49,53,59,69 , and N2 adsorption measurements 37,38,[47][48][49]53,58,59,61,63,68,69,73 (sometimes in conjunction with simulations 37,49,61,67,73 ). While indirect, this approach has proven to be valuable for detecting defects and assessing their concentration via simple semi-quantitative data analysis methods 37,49 .…”

Synthetic strategies to incorporate Ru-terpyridyl water oxidation catalysts into MOFs: direct synthesis vs. post-synthetic approach

“…51 A notable report from Wang et al demonstrates how the BET surface area in UiO-66 grows with increasing defects up to a threshold amount, but then begins to drop. 52 It appears that the amount of missing-linker defects in our edba-MOF samples is above this threshold. This conclusion is corroborated by the fact that the BET surface areas for both morphologies increase significantly upon incorporation of the Ru (tda) linkers, and Ru-edba-MOF 5 and 6 exhibit a surface area of 1390 m 2 g −1 and 800 m 2 g −1 , respectively.…”

What triggers dye adsorption by metal organic frameworks? The current perspectives

“…166 The reaction of MIL-101 (Cr) crystals with a high molar ratio of formic acid/CrCl 3 resulted in a better shape, larger surface area and effective adsorption performance in the MOF. [167][168][169] During the course of the synthesis, the addition of trifluoroacetic and HCl increased the adsorption capacity of the crystalline material. 170 Thus, it can be concluded that defects increase the surface area, expand the pore size and enhance the chemical stability of MOFs.…”