Ionothermal Synthesis Of Zirconium Phosphate Framework Materials And Their Gas Adsorption Properties

Zirconium phosphate materials have excellent properties due to their applications in the fields of adsorption, catalysis, ion exchange, and proton conductivity, etc. And the rational design and synthesis of zirconium phosphate materials with novel structures and compositions is important. Solvent arid organic template are two important factors in the synthesis of zirconium phosphate, therefore, how to design and choose new reaction mediums, better understanding the template effect of template agent in different solvents are crucial in the rational design and synthesis for the novel structure of such materials.Herein, a series of protic ionic eutectic mixture(protonated organic amine/oxalic acid) was selected and designed with an aim to synthesize novel zirconium phosphates using them as solvent and template by emerging ionothermal approach. The solvent effect and template-framework interaction have been studied in detail, and the different organic amine cations were studied with regard to their template effect to zirconium phosphate framework, as a result, a series of zirconium phosphates with 3D open framework were synthesized and their gas adsorption properties were also investigated. In addition, a series of novel zirconium phosphate materials using protic ionic liquids (organic amine to form a PIL with acetic acid) as solvent and template by emerging ionothermal approach. The final examples were characterized by powder XRD、SEM、TG and CHN methods. The main findings are as follows:1、Three different zirconium phosphate framework materials have been respectively synthesized in protic ionic eutectic mixture composed of oxalic acid/trimethylamine hydrochloride, oxalic acid dehydrate/dimethylamine hydrochloride and acid dehydrate/methylamine hydrochloride. And the P/Zr has an important effect to the final phase of zirconium phosphates. Interestingly, ZrPOF-TMA1 and ZrPOF-TMA2 are known zirconium phosphates, with 8-/10-ring channels and 7-/8-ring channels, respectively; ZrPOF-MA1 is an unknown phase and its crystal structure will be further solved, and they all have a relatively high thermal stability. Powder XRD, TG analysis and CHN elemental analysis showed that the protonated organic amine cations(TMA+、 DMA+、MA+) as a template were occluded in the frameworks of the compounds to keep the charge balance and also played a structure-directing role in crystallization process of zirconium phosphate. The organic templates in the channel of micropore zirconium phosphates were removed by calcination. The CO2 and CH4 adsorption capacity of the materials was also tested. It found that the CO2 and CH4 adsorption capacity of zirconium phosphate materials with 7-/8-ring channels exhibited a effective pore size selective behavior, for example, the CO2/CH4 adsorption ratio of ZrPOF-TMA2 was 12.7 at 1 bar, but the CO2/CH4 adsorption ratio of ZrPOF-TMAl was only 1.5 at 1 bar.2. Three protic ionic liquids(PILs) DETA(Ac)3, TETA(Ac)4 and TEPA(Ac)5 were respectively synthesized by using acetic acid to protonate organic polyamines. Then, four zirconium phosphate materials with different frameworks, denoted as ZrPOF-DETAl, ZrPOF-TETAl, ZrPOF-TEPAl and NH4Zr2(PO4)3, respectively, have been synthesized using these PILs as solvent and template by emerging ionothermal approach. The first three zirconium phosphate crystals are unknown phases, and they all have a lower thermal stability(300 ℃). Powder XRD, TG analysis and CHN elemental analysis showed that the organic cations of the PILs were not decomposed 4n crystallization process. DETA+、TETA+ and TEPA+ were respectively occluded in the framework of the zirconium phosphates to keep the charge balance and the different organic cations induced to generate different frameworks of zirconium phosphate.