Construction of Single Ni Atom-Immobilized ZIF-8 with Ordered Hierarchical Pore Structures for Selective CO₂ Photoreduction

Abstract

The rational construction of single-atom-modified porous metal–organic frameworks (MOFs) for efficient CO2 photoconversion is a promising avenue, yet the one that poses a significant challenge. In this study, we demonstrate the successful construction of a Ni single-atom-immobilized ZIF-8 with an ordered hierarchical (macro–micro) pore structure for highly efficient photocatalytic CO2 reduction to CO. The interpenetrated macroporous structure in microporous ZIF-8 is built up by employing polystyrene (PS) opal as a hard template, while the high stability of the framework is achieved through the double-solvent-induced crystallization. The hierarchical porous structure enables rapid mass transport and strong adsorption of CO2, while Ni single atoms as active sites and electron-trapping sites optimize the reaction energy and hinder the competitive H2 evolution. As a result, the Ni single-atom-immobilized hierarchical porous ZIF-8 achieves high stability and an activity of 4.2 mmol g–1 h–1 for CO yield with an electronic selectivity of 94%, which shows a 47-fold CO yield of that for ZIF-8. This work highlights the significance of constructing a hierarchical porous structure of MOFs and single-atom-active sites to improve the activity and selectivity of CO2 photoreduction for realizing carbon neutralization.

Enhancing CO2 photoreduction through unique 2D MOF-based heterostructures with metalloid doping

“…Additionally, the XRD analysis of pure ZIF-8 was consistent with previously reported data. 34 Upon the introduction of CuO into ZIF-8, both CuO and ZIF-8 peaks were evident, confirming their coexistence in the hybrids. After sulfidation, the CuS peaks were not clearly detectable, possibly due to their low generation amount and low crystallinity.…”

“…The analysis reveals that the morphology and crystal properties remain largely unchanged compared to the original sample, confirming the commendable stability of the CuS@CuO@ZIF-8NS photocatalyst. To evaluate the photocatalytic CO 2 reduction performance of the as-prepared CuS@CuO@ZIF-8NS, the CO 2 photoreduction performances of reported MOF-based photocatalysts and our work were compared as shown in Table S7 † 51–59 . It is notable that the CuS@CuO@ZIF-8NS catalyst possesses much higher yield rates of CO and selectivity of CH 4 , indicating its superiority for CO 2 photoreduction.…”

Enhanced Charge Transfer Process and Photocatalytic Activity over a Phosphonate‐based MOF via Amorphization Strategy

“…As displayed in the Fe K-edge X-ray absorption near edge structure (XANES) spectra (Figure 2a), the pre-edge peak at around 7114 eV belongs to a dipole-forbidden but quadrupole-allowed transition (1 s-to-3d) of the Fe center with distorted octahedral geometry, and the increased intensity for a-FePPA indicates a more distorted octahedral geometry. [8] The main peak at 7123 eV is attributed to the 1s-to-4p transition, which is nearly the same for a-FePPA and c-FePPA as that for Fe 2 O 3 , suggesting that the valence states for Fe in the two samples are close to + 3 oxidation state. [8b,9] Besides, the oxidation states of Fe center were further accurately evaluated by the first-order derivatives of the XANES spectra (Figure S4).…”

Mesopore and macropore engineering in metal–organic frameworks for energy environment-related applications

“…250 Recently, heterogeneous photocatalysts containing TiO 2 , ZnO, CdS, and Ni single atoms have been widely explored in environment treatment especially for photocatalytic CO 2 conversion/reduction and water splitting. 251,252,256 Mesoporous MIL-101 is well known for the specific adsorption of gas molecules (such as CO 2 ) and may promote its applications in the CO 2 photocatalysis reaction. Benefitting from the mesopores in MIL-101, Deng's group 253 recently created ‘molecular compartments’ inside MOF crystals by introducing TiO 2 inside as the active site for CO 2 photocatalysis.…”