Rational Design of Novel COF/MOF S-Scheme Heterojunction Photocatalyst for Boosting CO₂ Reduction at Gas–Solid Interface

Abstract

Solar-driven photoreduction of CO2 into valuable fuels offers a sustainable technology to relieve the energy crisis as well as the greenhouse effect. Yet the exploration of highly efficient, selective, stable, and environmental benign photocatalysts for CO2 reduction remains a major issue and challenge. The interfacial engineering of heterojunction photocatalysts could be a valid approach to boost the efficiency of the catalytic process. Herein, we propose a novel covalent organic framework/metal organic framework (COF/MOF) heterojunction photocatalyst, using olefin (CC) linked covalent organic framework (TTCOF) and NH2–UiO-66 (Zr) (NUZ) as representative building blocks, for enhanced CO2 reduction to CO. The optimized TTCOF/NUZ exhibited a superior CO yield (6.56 μmol g–1 h–1) in gas–solid system when irradiated by visible light and only with H2O (g) as weak reductant, and it was 4.4 and 5 times higher than pristine TTCOF and NUZ, respectively. The photogenerated electrons transfer route was proposed to follow the typical step-scheme (S-scheme), which was affirmed by XPS, in situ XPS and EPR characterizations. The boosting CO2 photoreduction activity could be credited to the special charge carrier separation in S-scheme heterojunction, which can accelerate photogenerated electrons transportation and improve the redox ability at the interface. This work paves the way for the design and preparation of novel COF/MOF S-scheme heterostructure photocatalysts for CO2 reduction.

Designing covalent organic frameworks with Co-O4 atomic sites for efficient CO2 photoreduction

“…In detail, the O 1 s peak of Co-2,3-DHTA-COF was deconvoluted into three peaks (Fig. 3a ): one at 531.9 eV for C-O-H 35 , one at 533.1 eV for Co-O-H and one at 533.7 eV for C-O-Co 10 . 2,3-DHTA-COF would exhibit a typical C-O-H peak at 532.2 eV 36 .…”

Metal–organic frameworks in photocatalytic Z-scheme heterojunctions: an emerging technology

“…94 The S-scheme formed at the interface of the composite of olefin linked TTCOF and NH 2 -UiO-66 (Zr) improved the transportation of photogenerated electrons and redox ability, thus enhancing photocatalytic CO 2 conversion to CO displaying a yield of 6.56 mmol g À1 h À1 . 95 In continuation with the band bending feature of photocatalytic systems, the photoelectrocatalytic (PEC) configuration has also shown promising performance. PECs operate on the same concept as Z-scheme photocatalysis by mimicking natural photosynthesis.…”

“…94 The S-scheme formed at the interface of the composite of olefin linked TTCOF and NH 2 -UiO-66 (Zr) improved the transportation of photogenerated electrons and redox ability, thus enhancing photocatalytic CO 2 conversion to CO displaying a yield of 6.56 μmol g −1 h −1 . 95…”

MOF/COF hybrids as next generation materials for energy and biomedical applications

“…This is because the hybrid photocatalyst has provided an increased surface area (900 m 2 g −1 ) which enhanced the transport of photogenerated carriers and their redox ability. 53 A hollow carbon electrocatalyst, Pt-COF@MOF 800 , was obtained through the pyrolysis of TP-BPY-COF@ZIF-8 and showed enhanced catalytic conversion and selectivity due to smooth mass transport and large number of active sites for oxygen reduction reaction. Moreover, the hollow carbon electrocatalyst preserved its long-term stability both in alkaline and acidic environments.…”