Covalent organic frameworks (COFs) are porous materials with tunable properties that can be useful in, e.g., catalysis, gas storage/separation, and optoelectronics. Incorporating metals can improve their properties for these applications. 2D networks can be built, for example, from metalated porphyrins or phthalocyanines. However, the metalation of 3D COFs without compromising the porous structure is much more challenging.

Psaras L. McGrier and colleagues, Ohio State University, Columbus, OH, USA, have metalated a three-dimensional COF with nickel for the first time. The team prepared the COF, called DBA-3D-COF, with a solvothermal synthesis combing a dehydrobenzoannulene (DBA) and tetra-(4-dihydroxyborylphenyl)methane (TBPM). The framework was then metalated using a solution of Ni(COD)₂ (COD = 1,5-cyclooctadiene) in toluene (10 wt%) to give the desired product (detail pictured) as a dark purple powder.

The metalated COF was characterized using X-ray crystallography, ¹³C NMR spectroscopy, X-ray photoelectron spectroscopy, and gas absorption measurements, amongst other techniques. The material retained its crystalline structure upon nickel insertion and the surface area was only minimally reduced. According to the researchers, nickel could be replaced with other metals, and metalated DBA-based COFs could be promising materials for application.

• Metalation of a Mesoporous Three-Dimensional Covalent Organic Framework,
  Luke A. Baldwin, Jonathan W. Crowe, David A. Pyles, Psaras L. McGrier,
  J. Am. Chem. Soc. 2016.
  DOI: 10.1021/jacs.6b10316