What is the optimum pH value for the synthesis of Co- succinate and Ni -succinate frameworks in aqueous solution? What are the optimum experimental conditions for reactants species?
Yes, pH value is important (e.g. first three links) as well as other conditions.
Co-succinate conditions (4th link).
Ni-succinate (5th link).
http://onlinelibrary.wiley.com/doi/10.1002/cplu.201402340/abstract
http://www.mdpi.com/1996-1944/7/4/3198
http://pubs.rsc.org/en/content/articlehtml/2015/cs/c4cs00230j
http://pubs.acs.org/doi/abs/10.1021/cm001148k
http://qap2.onlinelibrary.wiley.com/doi/10.1002/1521-3757%2820020201%29114:3%3C475::AID-ANGE475%3E3.0.CO;2-A/full
Of course, pH level is important, but the influence depends on the nature of linkers you use. Anyway, too low pH will prevent N,N ligands like 4,4'-bipy of bps from acting as linkers due to protonation; the same is valid for dicarboxylic acids. Though, in some cases, controlling the pH may make such linkers as tartaric acid to behave differently (involving -OH groups or not).
MOF synthesis is, at the heart of it, an acid-base reaction involving acidic metal ions and basic organic linkers (predominantly carboxylate, imidazolate, and pyridyl-based linkers). As Sergey described above, too low of a pH will prevent N-donor ligands from coordinating due to protonation. Similarly, anionic ligands (I shall use carboxylates as the example) form too slowly for effective synthesis of MOFs at low pH due to lack of deprotonation of the carboxylic acid precursors. Furthermore, too high of a pH may result in deprotonation of carboxylic acid occurring too quickly and producing low quality samples due to reduced opportunities for self-healing.
I suggest for pH optimization; We should know the ionization level of organic linker used as well as metal ion species at different pH and this depend on the pKa values.
@ Sergey A Adonin
so please what we can say about synthesis of MIL-129 based on nitrate d'aluminium and azobenzene dicarboxylic acid on PH 2.0 and 0.9 after synthesis?
thank you.
Sergey A Adonin
We can see the change in PH before and after any synthesis; in this case, the values appear rational to me, considering the nature of the ligand, metal, and solvent.
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