Synthesis by extrusion: continuous, large-scale preparation of MOFs using little or no solvent† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c4sc03217a Click here for additional data file.

Continuous flow mechanochemical and melt-phase synthesis at kg h–1 rates from solid reagents and either no solvent, or only minimal solvent, is reported.


General aspects Extrusion
Twin screw extrusion (TSE) was carried out using either a Thermo Fisher Process 11 Parallel Co-Rotating twin screw extruder, with an l/d ratio of 25, or a Haake Rheomex OS PTW16 co-rotating twin screw extruder with an l/d ratio of 40:1. Screw speeds were varied from 55 -250 rpm and the temperature from ambient to 200 0 C. Single screw extrusion (SSE) was conducted with a Dr. Collin E 25M single screw extruder with a l/d ratio of 25 at a screw speed of 30 rpm using a 25 mm diameter PTFE screw of constantly increasing root diameter.

Materials and Measurements
All materials were obtained from Sigma Aldrich UK in >98% purity or Molekula in >96% purity and were used as obtained without further purification. PXRD measurements were carried out on a PANanalytical X'Pert Pro X-ray diffractometer. Copper was used as the Xray source with a wavelength of 1.5405 Å. All experiments were carried out ex-situ using a spinning stage. Diffractograms were typically obtained from 5-50° with a step size of 0.0167°. Solution state NMR spectra were recorded on a Bruker AM 300 MHz referenced to the residual 1 H containing solvent. Chemical shifts (δ) are given in parts per million (ppm) and coupling constants in Hertz (Hz). In situ activation of compounds prior to Brunauer-Emmett-Teller (BET) analysis involved in situ heating at 200 0 C under vacuum for 2 hours. N 2 adsorption isotherms were obtained at -196 0 C between relative pressures (p/p 0 ) of 0.005 to 0.995, using a QuantaChrome Nova 4200e Surface area analyser. Total pore volume was obtained at p/p 0 = 0.995. Elemental analyses were determined by the Analytical Service department of the School of Chemistry and Chemical Engineering (ASEP) using a Perkin-Elmer 2400 CHN microanalyser.

Synthesis of trans-[Ni(NCS) 2 (PPh 3 ) 2 ]
Nickel(II) thiocyanate (5 g, 0.0285 moles), triphenylphosphine (14.98 g, 0.0572 moles) and methanol (HPLC grade, 0.0112 moles, 0.57 mL) were mixed together by hand for 30 seconds. The mixture was fed manually into a ThermoFisher Process 11 Extruder, at a screw speed of 55 rpm (residence time ca. 1.5 -2 minutes) to give an orange powder extrudate whose PXRD pattern was very similar to that of the simulated pattern simulated from the single crystal X-ray diffraction data of trans-[Ni(NCS) 2 (PPh 3 ) 2 ] (Figure 3). A small sample was heated to 80 o C for 2h to remove any volatiles before solution NMR analysis.
NMR data were consistent with literature data (Figures 4 and 5)..

Synthesis of Cu 3 (BTC) 2 (HKUST-1)
Copper(II) hydroxide (0.43 moles, 42.0 g), benzene-1, 3, 5-tricarboxylic acid (58.0 g, 0.286 moles) and industrial alcohol (99.9%, 60 ml) were mixed by hand for 30 seconds and fed manually into a ThermoFisher Process 11 at a screw speed of 135 rpm. A light blue powder extrudate was obtained whose PXRD pattern was similar to that simulated from the single crystal data for Cu 3 (BTC) 2 ( Figure 6). 1g of extrudate was stirred for 20 minutes in absolute ethanol (8 ml) and collected by filtration, three times. Oven-drying at 150 o C for 2 hours produced a dark purple solid. Similar PXRD patterns were obtained for products formed at screw speeds of 55-250 rpm ( Figure 6). N 2 BET Surface area: 1738 m 2 g -1 ; pore volume: 0.834 cm 3 g -1 .   FAWCEN). Activation was carried out by stirring a 5g sample in 40 mL HPLC grade methanol for 2 hours and filtering. This procedure was carried out twice. The resulting solid was oven-dried at 150 0 C for 2 hours. PXRD patterns for the activated products obtained at the various screw speeds were very similar to the simulated PXRD trace for ZIF-8 ) (Figure 8). N 2 BET Surface area: 1603.5 m 2 g -1 ; pore volume = 0.7065 cm 3 g -1 .

Synthesis of Al(fumarate)(OH)
Al 2 (SO 4 ) 3 ·18H 2 O (74.48 g, 0.11 mol), fumaric acid (25.94 g, 0.22 mol) and NaOH (pellets, 26.64 g, 0.66 mol) were pre-mixed for 30 seconds and fed manually into a Haake Rheomex 16mm twin screw extruder at room temperature, a screw speed of 55 rpm and a feed rate of 10g.min -1 . Activation was carried out by washing 1 g of product three times with H 2 O (30 ml) for 20 min. The XRD pattern of the activated product showed only the diffraction peaks corresponding to Al(OH)fumarate ( Figure 12). N 2 BET surface area: 1010 m 2 g -1 . with that reported in the literature 1 (above).