Manipulating micro-electric field and coordination-saturated site configuration boosted activity and safety of frustrated single-atom Cu/O Lewis pair for acetylene hydrochlorination

Abstract

Simultaneously boosting acetylene hydrochlorination activity and avoiding formation of explosive copper acetylide over Cu-based catalyst, which represented a promising alternative to Hg-based and noble metal catalysts, remained challenging. Herein, we fabricated a frustrated single−atom Cu/O Lewis pair catalyst (Cu/O−FLP) by coupling epoxide group (C−O−C) with atom-dispersed Cu−cis−N2C2Cl center to address this challenge. The basic epoxy site modulated the electron-de cient state of Lewis-acidic Cu center and paired with the Cu−cis−N2C2Cl moiety to preferentially break HCl into different electronegative Cu−Clδ− and C−O−Hδ+ intermediates, which further induced both an extra localized electric eld to polarize acetylene and a upshift of the d-band center of catalyst, thereby promoting adsorption and enrichment of acetylene by enhancing the dipolar interaction between acetylene and active intermediates. Moreover, the generated Cu−Clδ− and C−O−Hδ+ drastically reduced the energy barrier of rate-limiting step and madevinyl chloride easier to desorb from the Lewis-basic oxygen-atom site rather than traditional Lewis-acidic Cu center. These superiorities ensured a higher activity of Cu/O-FLP compared with its counterparts. Meanwhile, preferential dissociation of HCl endowed single-atom Cu with the coordination-saturated con guration, which impeded formation of explosive copper acetylide by avoiding the direct interaction between Cu and acetylene, ensuring the intrinsic safety during catalysis.

Advances in Single-Atom-Catalyzed Acetylene Hydrochlorination

“…It is widely acknowledged that metallic copper is prone to react with the reactant acetylene, forming acetylene-copper complexes that carry a high risk of explosion. To counter this process, Dai et al 32 addressed this concern by integrating the epoxy group (C−O− C) with atomically dispersed Cu-cis-N 2 C 2 Cl centers, resulting in the synthesis of a frustrated single-atom Cu/O Lewis pair catalyst (Cu/O-FLP). As depicted in Figure 9h, the Cu and O sites of this catalyst preferentially adsorb HCl, subsequently dissociating to form Cu−Cl and C−O−H active species.…”

“…(h) Schematic diagram of the vinyl chloride monomer formation route over Cu-cis-N 2 C 2 Cl–O 1 models with HCl and C 2 H 2 , preactivation. Adapted with permission from ref . Copyright 2023 Springer.…”

“…Meanwhile, more extensive exploration of other replacing catalysts only came into the spotlight after 2013. Among the various active metals including Ru, − Cu, − Pd, − Pt, ,, Ag, , and Fe, − Ru and Cu have received more attention probably owing to the balanced activity and price. Albeit the earlier works on these metals being mainly focused on particle catalysts, more and more recent studies point to the great potential of single-atom catalysts ,,− ,− ,,,− in acetylene hydrochlorination, rivaling the performance of the well-recognized gold counterparts and thus signifying a bright future for a mercury-free technology for PVC manufacture.…”

Progress in mercury-free catalysts for acetylene hydrochlorination

“…Peng et al fabricated a frustrated single-atom Cu/O Lewis pair catalyst (Cu/O-FLP) by coupling an epoxide group (C–O–C) with an atom-dispersed Cu– cis -N 2 C 2 Cl center. 68 The basic epoxy site modulated the electron-deficient state of the Lewis-acidic Cu center and paired with the Cu– cis -N 2 C 2 Cl moiety to preferentially break HCl into different electronegative Cu–Cl δ − and C–O–H δ + intermediates, which further induced both an extra localized electric field to polarize acetylene and an upshift of the d-band center of the catalyst. As a result, the Cu/O-FLP promoted the adsorption and enrichment of acetylene by increasing the dipolar interaction between acetylene and active intermediates.…”

Role of a Doped Support Strategy for Maintaining Stable Cun+ Sites in Acetylene Hydrochlorination

“…All the above catalysts exhibit excellent catalytic performance, but their industrial application is limited due to their high cost. In recent years, catalyst loading with Cu active sites has been developed and is attractive from the viewpoints of economic efficiency and environmental protection. − …”