Green and scalable approaches for synthesis and encapsulating clean metal nanoclusters inside cerium MOFs for efficient glycerol carboxylation with CO2

Abstract

In the pursuit of CO₂-neutral renewable energy solutions, biofuels have emerged as one of the key strategies. However, biodiesel production generates a surplus of crude glycerol (GL), creating a need for efficient valorization pathways. The conversion of GL into value-added chemicals represents a sustainable approach to address this issue. Metal nanoclusters (NCats) embedded within metal-organic frameworks (MOFs) constitute a promising class of hybrid catalysts for GL–CO₂ coupling, yet their controlled synthesis remains limited to a few MOF systems. Herein, we present a clean, scalable, and efficient method for the synthesis of ultra-small, surfactant-free Cu, Ag, and Pd NCats encapsulated in cerium-based MOFs. The resulting catalysts were evaluated in the direct carboxylation of crude GL with CO₂. Among them, the Pd₁Cu₁@MOF1 composite demonstrated outstanding performance, achieving > 73 % yield and a TOF > 100 h⁻¹ with pure GL, and > 14 % yield with a TOF of 30 h⁻¹ using crude GL. The method also enabled successful incorporation of trimetallic PdAgCu NCats, highlighting its potential for the sustainable synthesis of multimetallic NCats-MOF catalytic systems.