# Heterobinuclear Molecular Precursors Direct the Formation of Supported Subnanometer Cu–M Clusters with Tunable Catalytic Behavior

## TL;DR

Researchers developed a method to create tiny bimetallic clusters with tunable properties for better catalytic performance.

## Contribution

A new surface-anchored molecular approach enables precise synthesis of subnanometer Cu–M clusters with tunable catalytic behavior.

## Key findings

- Cu–M clusters (M = Ru, Mo, W, Fe) were synthesized on mesoporous silica using NHC-based precursors.
- Cluster composition is controlled by metal–metal bond stability in the precursor.
- CuRu and CuW clusters showed lower activation energy in ethylene hydrogenation than monometallic Cu.

## Abstract

Subnanometer bimetallic
clusters hold great promise for
catalytic
applications due to their unique electronic properties and high surface-to-volume
ratios. However, precise control over their composition and size remains
a major challenge, particularly for immiscible metal pairs. Here,
we report a surface-anchored molecular approach for synthesizing ∼0.7–0.8
nm Cu–M (M = Ru, Mo, W, Fe) bimetallic clusters on mesoporous
silica supports, using heterobinuclear N-heterocyclic carbene (NHC)-based
complexes as precursors. The NHC ligand functionalized with an alkoxysilane
anchor enables robust grafting to the silica interface. Controlled
calcination and reduction lead to subnanometer clusters with tunable
composition, dictated by the metal–metal bond stability in
the precursor. In situ transmission electron microscopy reveals cluster
growth proceeds via sintering of adjacent surface-bound units, while
elevated temperatures above 300 °C triggering diffusion and phase
separation. Catalytic testing in ethylene hydrogenation demonstrates
composition-dependent activity and kinetics, with CuRu and CuW clusters
exhibiting lower apparent activation energy barriers compared with
monometallic Cu nanoparticles. This study establishes a generalizable
strategy for the interfacial synthesis of alloyed clusters from molecular
precursors and provides mechanistic insight into how precursor design
governs nanostructure formation and catalytic behavior.