Cu(I)-Enriched Hierarchical HKUST-1/GO Composite: A Recyclable Catalyst for Green Azide–Alkyne Click Reactions

A simple and scalable template-assisted strategy for synthesis of graphene oxide (GO)-supported HKUST-1 MOF composite (HKUST-1/GO) as an efficient, recyclable, heterogeneous catalyst for azide-alkyne “Click” reaction is presented. Field emission scanning electron microscopy, powder X-ray diffraction, and X-ray photoelectron spectroscopy analysis suggest that the use of GO as a synthetic template promotes the growth of Cu(I)-rich hierarchical MOF structures with elongated, regular cuboidal shapes. Catalytic investigations over room temperature reaction of α-naphthyl azide with phenylacetylene-as a model azide-alkyne cycloaddition (AAC) click reaction, reveal the outstanding catalytic performance and recyclability of the HKUST-1/GO composite. Besides the model AAC reaction, the HKUST-1/GO composite is demonstrated to exhibit exceptionally high catalytic performance toward cycloaddition reaction of various sterically challenging and biologically relevant azide-alkyne systems. Our investigations demonstrate that the templated growth of Cu-MOF over GO imparts it with mixed valence active Cu catalytic sites, improved electronic conductivity, and a unique morphology that enables rapid analyte transport. These GO-induced features confer excellent stability, recyclability, and activity to the HKUST-1/GO composite. The exceptional catalytic performance, ease of recovery, and excellent recyclability as demonstrated for HKUST-1/GO composite in the present work position it as a cost-effective, efficient, and reusable heterogeneous catalyst for AAC click reactions.