Enhanced Catalytic Performance for the Ethynylation Reaction of Formaldehyde over a Silica-Coated Metal–Organic Framework HKUST-1-Derived Cu-Based Catalyst

1,4-Butynediol (BYD), produced by the ethynylation of formaldehyde, is an important organic chemical raw material that can be used to synthesize a variety of organic products. Copper-based catalysts commonly used to synthesize BYD face challenges in terms of activity and stability. In this study, an HKUST/SiO2-350 catalyst was synthesized using the sol–gel method based on the metal–organic framework material HKUST-1 for the ethynylation reaction of formaldehyde. The HKUST/SiO2-350 catalyst exhibits a stable porous structure, high surface area, and high copper dispersion, achieving the highest activity and copper utilization efficiency when used in the reaction. At a reaction temperature of 90 °C, the space-time yield of metallic copper for HKUST/SiO2-350 reaches 0.9744 gBYD·gCu–1·h–1, which is nearly 10 times higher than that of HKUST-1. After six cycles of reaction, no apparent deactivation was observed. The excellent performance of HKUST/SiO2-350 provides a valuable reference for designing catalysts for the ethynylation of formaldehyde.