A cytosine–silver incorporated metal–organic framework for efficient laccase-mimicking reactions

Nucleobases are essential components of nucleic acids and provide multiple coordination sites, making them useful ligands for metal-based catalysis. Purine-type nucleobases such as adenine and guanine have been widely studied because of their rigid structures and strong metal-binding ability, whereas the pyrimidine-type cytosine (Cyt) has seen far less use in catalysis. Here, we present a new catalyst: a Cu-based metal-organic framework (MOF) modified with the biocompatible nucleobase Cyt. Silver ions are chelated by the Cyt-Ag structure inside the MOF, forming a bimetallic nanozyme named HKUST-1-Cyt-Ag (HKUST = Hong Kong University of Science and Technology). This hybrid exhibits strong laccase-like activity, driven by the synergy between the Cu-based HKUST-1 framework and the Cyt-Ag motif. To our knowledge, this is the first demonstration of ligand-chelating metalation in HKUST-1, highlighting its potential to mimic multicopper oxidase activity for biocatalytic applications.