(2014) 'Crystal growth of MOF-5 using secondary building units studied by in situ atomic force microscopy. ', CrystEngComm., 16 (42). pp. 9834-9841. Further information on publisher's website:https://doi.org/10.1039/C4CE01710BPublisher's copyright statement:Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Crystal growth of the metal-organic framework, MOF-5, using basic zinc benzoate, [Zn 4 O(O 2 CC 6 H 5 ) 6 ], was studied in real time using atomic force microscopy. The twodimensional nuclei involved in layer growth were found to form by a two-step process whereby 1,4-benzenedicarboxylate units first attach to the MOF-5 surface followed by addition of a layer of Zn species and connecting 1,4-benzenedicarboxylate units. 6 ]-containing growth solutions were found to influence the relative growth rates along different crystallographic directions and to lead to a faster nucleation rate under certain conditions when compared to growth solutions containing simpler zinc salts. This suggests a degree of remnant association of the zinc species derived from the [Zn 4 O(O 2 CC 6 H 5 ) 6 ] cluster during crystal growth under these conditions. IntroductionPorous metal-organic frameworks (MOFs) are formed from the connection of metal ions and organic linkers to provide an enormous number of different structures of varying pore dimension, geometry and functionality that are finding potential use in a diverse array of new and traditional applications. [1][2][3][4] Considerable effort has been expended to optimise the synthesis of these materials with regards to numerous factors including: yield, crystal size, morphological control, the rate of product formation and the synthesis temperature. One such approach to the synthesis of MOFs is the so called "controlled secondary building unit (SBU) approach" (CSA) introduced by Serre et al. 5 The rationale behind the development of this approach was that MOF syntheses could be speeded up if the metal components added to the reaction solution were already preassembled to resemble the SBUs of the final crystalline MOF. This method has succeeded in decreasing reaction times and temperatures for several MOFs,[5][6][7] in addition to proving to be very useful in the synthesis of nanoparticles, 8 thin films, 9 and producing MOF homologues with new metal content. 6One of the questions arising from the CSA methodology is whether the SBU remains intact during synthesis. If it does then this would suggest that formation of the MOF can occur via a simple ligand substitution ...