  Two dimensional pi conjugated metal porphyrin covalent organic frameworks
were produced in aqueous solution on an iodine-modified Au(111) surface by on
site azomethine coupling of Fe(III) 5,10,15,20 tetrakis(4 aminophenyl)porphyrin
(FeTAPP) with terephthal dicarboxaldehyde and investigated in detail using
in-situ scanning tunneling microscopy. Mixed covalent organic porphyrin
frameworks consisting of FeTAPP and metal-free TAPP (H2TAPP) were prepared
through simultaneous adsorption in a mixed solution as well as partial
replacement of FeTAPP by H2TAPP in an as prepared metal porphyrin framework. In
the mixed framework, the relative distribution of FeTAPP to H2TAPP was not
random and revealed a preference for homo-connection rather than
heteroconnection. The construction of substrate-supported, pi conjugated
covalent frameworks from multiple building blocks, including metal centers,
will be of significant utility in the design of functional molecular
nanoarchitectures.

Materials Science