Exploiting Reaction‐Diffusion Conditions to Trigger Pathway Complexity in the Growth of a MOF

Abstract

Coordination polymers (CPs), including metal–organic frameworks (MOFs), are crystalline materials with promising applications in electronics, magnetism, catalysis, and gas storage/separation. However, the mechanisms and pathways underlying their formation remain largely undisclosed. Herein, we demonstrate that diffusion‐controlled mixing of reagents at the very early stages of the crystallization process (i.e., within ≈40 ms), achieved by using continuous‐flow microfluidic devices, can be used to enable novel crystallization pathways of a prototypical spin‐crossover MOF towards its thermodynamic product. In particular, two distinct and unprecedented nucleation‐growth pathways were experimentally observed when crystallization was triggered under microfluidic mixing. Full‐atom molecular dynamics simulations also confirm the occurrence of these two distinct pathways during crystal growth. In sharp contrast, a crystallization by particle attachment was observed under bulk (turbulent) mixing. These unprecedented results provide a sound basis for understanding the growth of CPs and open up new avenues for the engineering of porous materials by using out‐of‐equilibrium conditions.

A Hexagonal Nut‐Like Metal–Organic Framework and Its Conformal Transformation

“…Note that the intermediates collected at t ≧ 120 min show additional signal from (2−01) and (131) planes, indicative of the growth of the high‐index facets, while the intermediate collected at 1 min displayed signal at q = 0.024 Å −1 (2θ = 0.34°), indicative of ordered superstructure caused by the crystallization by particle attachment (Figure 2f). [ 37–39 ] This is also the first case to prove the existence of a superstructure during the formation of MOF through the one‐pot synthesis method. With increasing the reaction time, the peak intensity at 2θ = 0.34° gradually decreased, which is in accordance with the SEM and TEM observations.…”

Enabling Technology for Supramolecular Chemistry

“… Examples of supramolecular species and precursors and self-assembly processes that have been examined or enhanced using enabling technology for process control ( Puigmartí-Luis et al, 2010 ; Numata et al, 2015a ; Rubio-Martinez et al, 2016b ; Gong et al, 2016 ; Thorne et al, 2019 ; Puigmarti-Luis et al, 2021 , This figure contains an image of Figure 2a from Thorne et al that has been used to make this composite figure under the terms of a Creative Commons Attribution 4.0 International License https://creativecommons.org/licenses/by/4.0/ ), screening ( Greenaway et al, 2018 ), optimisation ( Jones et al, 2021 , The flow diagram and crystal structures in the optimization panel have been reused from Figure 2 and 11 from https://pubs.acs.org/doi/abs/10.1021/jacs.1c02891 respectively with permission from the ACS. Further permission related to the material excerpted should be redirected to the ACS), and scale up ( Briggs et al, 2015 ; Rubio-Martinez et al, 2016a ).…”

“…Flow chemistry offers benefits such as improved safety and control of reactions, access to a wider range of reaction conditions, easier scale-up, and potential savings in energy use and wastage ( Newman and Jensen, 2013 ). Early adopters of continuous flow chemistry within the supramolecular community used microfluidic chips to influence process outcome ( Whitesides, 2006 ; Zhang et al, 2012 ; Foster et al, 2015 ; Parker et al, 2015 ; Yu et al, 2015 ; Gong et al, 2016 ); significant progress in flow technology has since opened a wealth of new opportunities for the field ( Arnon et al, 2016 ; Fang et al, 2018 ; Cohen-Gerassi et al, 2020 ; Méndez-Ardoy et al, 2020 ; Khoeini et al, 2021 ; Puigmarti-Luis et al, 2021 ).…”

Flow-Assisted Selective Mineral Extraction from Seawater

“…The laminar coflow method (LCM) presents an alternate route to drive reactions far from the thermodynamic equilibrium without the need for heat energy, electric fields, or complex chemical reagents. , One of the main advantages of LCM is the ability to generate and maintain a reactive interface , with steep concentration and pH gradients (inset of Figure a). The gradients influence precipitation dynamics and ion transport at the interface, which can greatly affect the complexity of reaction pathways . Such gradients are transient and decay quickly in the absence of controlled fluid flow, as is the case with stirred bulk mixing.…”