# Constructing Z‑Scheme Ni-MOF-74/CoAl-Layered Double Hydroxide Heterojunctions for Enhanced Photocatalytic CO2 Reduction

## TL;DR

This study creates a Z-scheme heterojunction using Ni-MOF-74 and CoAl-LDH to improve photocatalytic CO2 reduction, achieving a 70% increase in CO production.

## Contribution

A new strategy for constructing Z-scheme heterojunctions using Ni-MOF-74 as a template for CoAl-LDH nanosheets.

## Key findings

- 20-NiL shows a CO production rate of 79.86 μmol·g–1·h–1, a 70% improvement over pristine components.
- XPS confirms electron transfer from CoAl-LDH to Ni-MOF-74 under light irradiation.
- In situ spectroscopy reveals a 2e– pathway for CO2 conversion to CO via COOH* and CO* intermediates.

## Abstract

Constructing Z-scheme heterojunctions
is crucial
for improving the charge localization on the surface of photocatalysts
and enhancing photocatalytic reduction performance. Herein, this research
proposes a heterostructure construction strategy that utilizes a Nickel-based
metal organic framework with MOF-74 topology (Ni-MOF-74) as a structural
template for deriving ultrathin CoAl-LDH nanosheets (denoted as 20-NiL).
This approach enables precise control over the two-dimensional lamellar
morphology and interfacial electronic structure, facilitating electron–hole
pair separation and mitigating CoAl-LDH nanosheet aggregation. Under
simulated solar irradiation, 20-NiL exhibits a CO production rate
of 79.86 μmol·g–1·h–1, representing a 70% enhancement over the pristine components. By
comparing the XPS spectra before and after the photocatalytic reaction,
we confirm the charge transfer mechanism of the Z-scheme heterojunction: the binding energies of Co and Al increase,
while that of Ni decreases, indicating the transfer of electrons (e–) from CoAl-LDH to Ni-MOF-74 upon light irradiation.
In situ Fourier transform infrared spectroscopy combined with Soft
X-ray absorption spectroscopy elucidates the 2e– pathway for CO2 conversion to CO through the dominant
intermediates COOH* and CO*. This work is expected to provide helpful
reference for the development of Z-scheme heterojunction
photocatalysts and the investigation of their charge transfer kinetics.