A crystallisation facilitator for promoting crystal growth of a metal-organic framework, the crystallisation facilitator comprising at least one of: a metal or ionic form of that metal, or a compound including a metal, which is selected from the group consisting of Group 1 through 16 metals of the IUPAC Periodic Table of the Elements including actinides, and lanthanides, and combinations thereof. A method of synthesising a metal-organic framework using the crystallisation facilitator is also described.