Synthesis And Adsorption Properties Of UiO-66-NH₂ Base Metal-Organic Frameworks Composites

In this paper,metal organic framework composite material/membrane were successfully prepared,and the feasibility of the materials was verified by a series of characterization and experiments.The research results were as follows:1.3D-agaric like core-shell architecture UiO-66-NH2@ZIF-8 was synthesized using ZIF-8 with rich active sites and UiO-66-NH2(U6N)with good water stability as the matrix materials and polyvinylpyrrolidone(PVP)as the surfactant.The effects of PVP and methanol amount added on the morphology of composites and adsorption properties of REEs were investigated.Due to the abundant adsorption sites of ZIF-8 and the excellent water stability of UiO-66-NH2,3D-agaric like U6N@ZIF-8-20 showed quick adsorption rate(only 10 min to reach equilibrium),high adsorption capacity and selectivity for REEs from water compared to other reported adsorbents.Maximum adsorption capacities of U6N@ZIF-8-20 for neodymium(Nd(Ⅲ)),europium(Eu(Ⅲ)),gadolinium(Gd(Ⅲ))and erbium(Er(Ⅲ))achieved to 249.90,295.28,316.22 and 340.95 mg g-1,respectively.U6N@ZIF-8-20 has superiority in selective adsorption of REEs from Cd(Ⅱ),Zn(Ⅱ),Cu(Ⅱ),Mn(Ⅱ)and Co(Ⅱ)coexistence solution.The order of adsorption capacities for REEs is in agreement with the order of their electronegativity,ionic radius and charge density.Moreover,U6N@ZIF-8-20 showed better water stability and recyclability than single MOF.And after four cycles of elution,the adsorption capacities of U6N@ZIF-8-20 for REEs can still maintain more than 80%and the crystal structure is good,which proves that the composite material has good practical application value.2.In order to improve the shortcomings of poor cycle performance of powdery MOFs in liquid phase separation,functional metal-organic framework composite film TPU/0.1THB/U6N-1.5 was synthesized by electrostatic spinning using UiO-66-NH2 and polyurethane as raw materials.During the post-synthetic modification,3,4,5-trihydroxybenzaldehyde is used as modifier to introduce more hydroxyl groups.According to SEM,FTIR,XPS and XRD analysis,it was proved that TPU/0.1THB/U6N-1.5 was successfully synthesized.The adsorption data of Ga(Ⅲ)by TPU/0.1THB/U6N-1.5 is in accordance with the Langmuir and the pseudo-second-order kinetic models,and its maximum adsorption amount is 96.18 mg g-1 under optimum conditions(pH 10,the adsorption time 8 h,and temperature 25℃).The long-term filtration of TPU/0.1THB/U6N-1.5 has no significant effect on the water flux and metal ion removal rate,and the highest water flux can reach 1189.63 L m-2 h-1.TPU/0.1THB/U6N-1.5 can reach an adsorption capacity of about 90%after five cycles of elution.Meanwhile,it has excellent selective adsorption property for Ga(Ⅲ)in coexistence solution,indicating that TPU/0.1THB/U6N-1.5 has great application potential in liquid phase separation.And the stability of composite membrane has been greatly improved in recycling applications compared to the adsorbents.