Nickel−alkyne−functionalized metal−organic frameworks: An efficient and reusable catalyst

• The alkynes provide a platform to obtain site-isolated and unsaturated metal sites for catalytic application. • The alkyne is firstly introduced into the UiO-66-type metal-organic frameworks (UiO-66-alkyne). • The catalytic site of Ni is incorporated into MOF-alkyne by bonding with terminal alkynyl groups. • Ni-UiO-66-alkyne shows excellent catalytic performance and the promising industrialization characteristics. Electron-donating groups in the robust MOF motif are able to provide an excellent catalytic platform, therefore obtaining site-isolated metal sites. In this study, the terminal alkyne is firstly introduced into UiO-66-type metal-organic frameworks (UiO-66-alkyne). Herein, to further study the application potential of this material, a covalently bonded nickel catalyst based on the alkynyl-tagged UiO-66-alkyne has been prepared and afforded us unprecedented highly dispersed and highly efficient catalytic active species. Meanwhile, this nickel-contained catalyst method for joining metals provided an alternative pathway regarding catalyst designing. With UiO-66-alkyne-Ni, the heterogeneous transformation of homogeneous catalysts is realized. Using benzaldehyde and malononitrile as starting materials, we were able to catalyze the Knoevenagel condensation within 45 min under room temperature with yield (> 99 %). Moreover, the recovery rate of the UiO-66-alkyne-Ni also outperformed previous MOFs in both small-scale and gram-level reactions, which shows UiO-66-alkyne-Ni is a potential contributor to the subsequent industrialization.