Process for preparing shaped metal-organic framework materials

Abstract

A process for the preparation of a shaped MOF, the process comprising: providing a first reactant comprising at least one metal in ionic form and a second reactant comprising at least one organic ligand capable of associating with said metal in ionic form, and optionally a solvent; allowing the first and second reactants to react to form a MOF; and forming a shaped body directly from the mixture of step b) using an extruder or continuous kneader; wherein the initial ratio of the at least one metal in ionic form to the at least one organic ligand is controlled such that shaped bodies having a minimum defined crush strength are formed without the use of an external binder or lubricant.

Claims

1. A process for the preparation of a shaped MOF, the process comprising: a) providing a first reactant comprising at least one metal in ionic form and a second reactant comprising at least one organic ligand capable of associating with said metal in ionic form, and optionally a solvent; b) allowing the first and second reactants to react to form a MOF; and c) forming a shaped body directly from the mixture of step b) using an extruder or continuous kneader; wherein the initial ratio of the at least one metal in ionic form to the at least one organic ligand is controlled such that shaped bodies having a crush strength of at least 6.9 N/mm are formed without the use of an external binder or lubricant; and wherein there is a molar excess of 1-15% of the second reactant.

2. A process as claimed in claim 1, wherein the at least one metal is selected from Zn, Co, Mg, Cu, Al, Tb, Gd, Ce, La, Fe, Li, Sc, Mn, Cr, Ti, Zr, Ni, Si, and combinations thereof.

3. The process as claimed in claim 1, wherein the second reactant is an alkoxide, aryloxide, imidazole, imidazolate, carboxylate, pyridine, amine, carboxylic acid, diacid and/or triacid moiety.

4. The process of claim 1, wherein the shaped body is formed by the application of pressure at less than 100 bar (1,400.5 psi).

5. The process of claim 1, wherein each of steps a) to c) is performed on an extruder or continuous kneader.

6. The process of claim 1, wherein the process is a continuous process.

7. The process of claim 1, wherein the process is a one-step process.

8. The process of claim 1, wherein the second reactant is included at a molar excess of between 1.1 and 15%.

Description

DRAWINGS

(1) FIG. 1 shows crush strength of the CuBTC pellets as a function of TMA concentration.

EXAMPLES

(2) The following examples are not intended to limit the scope of the invention, which is defined by the appended claims, but are illustrative only.

(3) Materials and Methods

(4) Extrusion was performed on a Three Tex Extruder ZE-12 Model (AB-14-21375).

(5) Crush strength was measured according to ASTM D 6175-03.

Example 1

(6) Preparation of CuBTC (Copper Benzene-1,3,5-Tricarboxylate) Shaped Bodies

(7) Copper hydroxide (205 g, 2.1 moles) and Trimesic acid (309.5 g, 1.47 moles) (molar ratio 3:2.1) were blended in a v-blender for 30 minutes (molar excess of second reactant of 5%). This powder was added to the feeder of the extruder. The extruder screw speed was set to 150 rpm, the gravimetric feed rate was set to 5 g/min and the liquid flow rate to 3.5 ml/min. The extruder was set up with 2 mm die face to produce shaped pellets with 2 mm diameter. The pellets exiting the extruder were dried at 150° C. for 2 hours and then activated for 1 hour at 200° C.

(8) The measured BET surface area of the pellets was 1302 m.sup.2/g. Analysis of the composition of the pellets yielded a reading of 11.26 wt % trimesic acid.

(9) The crush strength of the pellets as measured by ASTM D 6175-03 was 8.84 N/mm.

Example 2

(10) Preparation of ZIF-8 Shaped Bodies

(11) Zinc Oxide (340 g, 4.18 mol) and 2-methyl imidazole (652 g, 7.94 mol) (molar excess of second reactant of 5.3%), were volumetrically fed into a Three Tec twin screw extruder at rate of 100 g/hr. A 0.5 M acetic acid in methanol solution was co-fed into a heated extruder barrel (50° C.) at a rate of 120 ml/hr. The co-rotating twin screws were operated at a speed of 100 rpm. The resulting extrudates were collected on a tray and dried in vacuum oven at 50° C. for 1 hour, with additional heat treatment at 150° C. for 16 hours. The activated extrudates yielded a BET surface area of 1736 m.sup.2/g, and radial crush strength (ASTM D 6175-03) of 10.4 N/mm.

Reference Example

(12) Preparation of CuBTC Shaped Bodies at Alternative Ratios

(13) The process of example 1 was repeated with Copper hydroxide (205 g, 2.1 moles) and Trimesic acid (294.75 g, 1.4 moles) at a molar ratio of 3:2 (i.e. stoichiometric). The pellet was subject to BET surface area analysis which gave a result of 1,650 m.sup.2/g. Measurement of the strength of the pellets by ASTM D 6175-03 gave a result of 1.3 N/mm. Analysis of the composition of the pellets yielded a weight percentage of 0.83% of trimesic acid.

(14) Evaluation of Trimesic Acid Content Versus Crush Strength

(15) The amount of trimesic acid present in the pellets was determined by titration of the trimesic acid against a standard sodium hydroxide solution. The trimesic acid in the pellets was first isolated by stirring of the pellets in methanol to extract them.

(16) A graph of the trimesic acid content versus crush strength is shown in FIG. 1.

(17) The results show that shaped bodies or pellets having sufficient crush strength for commercial application can be produced directly from the starting reactants for the MOF, and in the absence of an external binder or lubricant. Advantageously, this means that the resultant MOFs exhibit increased character of the MOF and retain high BET surface areas. Conversely, when the ratios of the starting materials are not carefully controlled, the resultant shaped bodies exhibited poor crush strength (i.e. <6.9 N/mm), and would typically require a binder or lubricant to be formed into commercially useful shaped bodies.