Kinetics study and crystallization process design for scale‐up of UiO‐66‐NH₂ synthesis

Abstract

A comprehensive scale-up procedure for amine-functionalized UiO-66 is implemented, which leads to the development of a novel flow-through metal-organic framework synthesis process. Products are characterized via BET modeling of N 2 adsorption at 77 K and powder XRD to confirm crystal porosity and phase, respectively. Batch syntheses are conducted to examine the effects of polytetrafluoroethylene and glass vessel materials on crystal yield and quality. Intermediate samples from sealed-vessel trials at 373, 383, and 393 K are collected and characterized, which show a high degree of product consistency. Nucleation rates are determined at the same temperatures, and the Arrhenius relationship is used to predict the activation energy of nucleation, E aNuc . A continuous-flow reactive crystallization process is developed using a draft-tube type reactor. As a proof of concept, the reactor is operated for three retention times. The cumulative product, material retained within the crystallizer, and intermediate samples are collected and characterized to confirm UiO-66-NH 2 production.

Impact of the Nature of the Organic Spacer on the Crystallization Kinetics of UiO‐66(Zr)‐Type MOFs

“…In contrast, the UiO‐66‐CH 3 and UiO‐66‐NO 2 solids possess E a values in the same order to those reported for other MOFs 10. The E calculated for UiO‐66‐NH 2 is 46(3) kJ mol −1 , which is lower than the reported value by Schoenecker et al 19. (64.5 kJ mol −1 ).…”

“…[10] The E a n calculated for UiO-66-NH 2 is 46(3) kJ mol À1 ,w hich is lower than the reported value by Schoeneckere tal. [19] (64.5 kJ mol À1 ). This could arise from the different conditions of crystallization studied (especially the addition of an excess of HCl).…”

Towards scalable and controlled synthesis of metal–organic framework materials using continuous flow reactors

“…There are also two reports of the use of continuous-stirred tank reactor for MOF syntheses, which could be optimised to give similar yields to the flow reactors: Schoenecker et al used a baffled reactor to produce UiO-66 from DMF solvent, 44 whereas McKinstry et al reported the synthesis of MOF-5 crystals in a continuous-stirred tank reactor and found that increased space-time-yields required 4 hour residence time. 45 Microfluidic synthesis of MOFs has also been the focus of some attention, which although not immediately scalable to produce materials at industrially viable levels, allows the fundamental variables defining continuous production to be investigated easily.…”

Continuous flow production of metal-organic frameworks

“…While it allows excellent control of the MOF's morphology, microfluidic processing is hampered by low quality of the final products and a low STY. Proof of concept meso-and macroscale flow production has also been reported [26 ,27 ,29 ,47 ], and pumped metering of a spacer ligand solution into a stirrer-tank reactor has been described [23,48,49]. Gimeno-Fabra et al showed that counter-current mixing of precursor solutions with water at the high temperature of 300 8C (Figure 3 Centre, Table 1) can lead to MOFs under hydrothermal conditions [26 ].…”