Hollow Mesoporous Organosilica Spheres Encapsulating PdAg Nanoparticles and Poly(Ethyleneimine) as Reusable Catalysts for CO₂ Hydrogenation to Formate

Abstract

CO2 hydrogenation to formic acid, a renewable hydrogen storage compound, has been regarded as a key reaction to realize hydrogen energy cycles. However, the development of robust heterogeneous catalysts with high activity and stability has been a challenge. We herein report a synthesis of hollow nanostructured composite consisting of PdAg nanoparticles (NPs) and aminopolymers, poly­(ethyleneimine) (PEI), confined in hollow mesoporous organosilica spheres (HMOSs), which act as an efficient and stable heterogeneous catalyst for hydrogenation of CO2 to formate. The catalyst exhibits high formate yield with a turnover number (TON) of over 2700 and 13 700 for 22 and 110 h, respectively, under mild reaction conditions (total 2.0 MPa, 100 °C), which outperforms the conventional supported Pd catalysts because of the cooperative action of PEI and PdAg NPs confined in a nanospace to directly capture, activate, and hydrogenate the CO2 molecule. The catalyst is reusable over multiple cycles with high activity because of the protective effect and alkali-tolerant property of HMOSs. This study offers a strategy for the design and development of an efficient and stable heterogeneous catalyst for CO2 conversion.

Heterogeneous catalysts for the hydrogenation of amine/alkali hydroxide solvent captured CO2 to formate: A review

“…95 1). 83 As shown in Fig. 5, the addition of Co into the Pd@MSN catalyst can increase the catalytic activity remarkably with Pd 0.8 Co 0.2 @MSN being the best-performed catalyst.…”

An air-stable, reusable Ni@Ni(OH)2nanocatalyst for CO2/bicarbonate hydrogenation to formate

“…[8][9][10][11][12][13][14][15] Among various transformation approaches, conversion of CO 2 to formic acid (FA) or formate attracts considerable attention. 1,[16][17][18][19][20][21][22] FA is an important precursor for multiple organic chemicals. 24 Additionally, FA has potential as a hydrogen storage medium for fuel cell applications.…”

Closing the Anthropogenic Chemical Carbon Cycle toward a Sustainable Future via CO2 Valorization

“…Pd-based NPs have demonstrated their attractive catalytic performance among various metal catalysts. The PdAg+PEI@HMOS catalyst composed of PdAg alloy NPs and poly(ethylenimine) (PEI) composite in hollow mesoporous organosilica spheres (HMOSs) (Figure 6a,b) was designed for the CO 2 reduction to formic acid; [100] the catalyst exhibited outstanding catalytic performance toward CO 2 hydrogenation with TOF up to 125 h −1 under mild reaction conditions (2.0 MPa, 100 °C). The outstanding CO 2 hydrogenation activity was ascribed to the synergetic effect between PEI and PdAg NPs, where PdAg NPs functioned as the active sites for hydrogenation and PEI acted as a CO 2 adsorbent to increase CO 2 concentration on the surface.…”

“…Reproduced with permission. [100] Copyright 2020, American Chemical Society. c) Fabrication pathway and d) TEM images of CuZn@UiO-bpy.…”

“…b) Synthetic procedure for PdAg+PEI@HMOS catalyst. Reproduced with permission [100]. Copyright 2020, American Chemical Society.…”