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Mimicking the natural photosynthesis process, photocatalytic conversion of CO 2 has been an ongoing hotspot of scientific research and technology development. A key aspect is the discovery of high potency catalysts for facilitating the multi-electron participated reactions. Herein we successfully demonstrate exfoliated nanosheets from a conductive 2D-MOF Ni 3 (HITP) 2 as an efficient co-catalyst for CO 2 reduction in a hybrid photocatalytic system under visible light illumination. By taking advantage of the high conductivity for charge transportation and highly accessible active sites for redox reactions, an excellent selectivity of 97% for deoxygenative CO 2 reduction and a high CO yield rate of 3.45 × 10 4 μmol·g −1  h −1 were achieved with superior stability. This work provides essential insights into future design and development of more effective MOFs-based systems for catalytic CO 2 utilization. [ABSTRACT FROM AUTHOR]

A hierarchical structure of CuCoNC arrays constructed on copper foam that enriches multiple active species on the MOF-based scaffolds simultaneously delivers extraordinary HER, OER and ORR performance, resulting in highly efficient overall water splitting powered by Zn-air batteries using the same single catalyst. • MOF-templated hierarchical CuCoNC arrays are constructed on copper foam. • Remarkable trifunctionality of OER, HER and ORR are achieved using a single catalyst. • Overall water splitting can be powered by using a single dry cell of 1.50 V. • Zinc-air batteries demonstrate highly energy efficiency >58% for over 360 h. • ZAB-powered water splitting is capable of producing H 2 in 69 μL s−1. Multifunctional electrocatalysts based on earth-abundant elements are key for the development of Integrated Energy Systems (IES) such as electrolytic water splitting powered by metal-air batteries. Herein, hierarchical CuCoNC nanowire arrays are constructed on copper foam, enriching multiple active species on the catalytic scaffolds that lead to remarkable trifunctional activities of OER with η 10 = 245 mV, HER with η 10 = 59 mV and ORR comparable to Pt/C. While for overall water splitting a cell voltage of only 1.78 V is required to achieve a high current density of 500 mA cm−2, for Zn-air batteries (ZABs) a highly stabilized round-trip efficiency of >58% is achieved for over 360 h under 10 mA cm−2. Ultimately, a highly efficient IES of ZAB-powered water splitting employing a single catalyst is demonstrated with a hydrogen evolution rate of 69 μL s−1, showcasing a smart material design in simultaneously achieving multi-functionality and maximizing the energy efficiency. [ABSTRACT FROM AUTHOR]

• Composite thin films comprising 2D/2D MOF/rGO heterostructures for photocatalytic CO 2 reduction. • Modulated electronic structure of metal centers unveiled by XPS and XANES. • The activity and selectivity are among the best reported in literature. • The thin-film catalysts are highly stable and extremely easy to recycle. • High activity is well rationalized by the heterostructure configuration and electrostatic charge transfer. In this work, composite thin films comprising the 2D/2D MOF/rGO heterostructures assembled via Coulomb interaction are employed as the cocatalyst for photocatalytic CO 2 reduction for the first time. The electrostatic charge transfer and the strong π-π interaction induced in the heterostructure effectively modulate the electronic structure of the metal centers in the conductive 2D MOF (Ni 3 HITP 2), evidenced by Zeta Potentials, HR-TEM, XPS and XANES. The best thin-film catalyst with an optimal MOF/rGO ratio demonstrates a high CO evolution rate of 3.8 × 104 μmol h−1 g film −1 (0.46 min−1 in TOF) and a good selectivity of 91.74%, synergically contributed by the improved photoelectron harvesting on the rGO scaffold, the efficient charge transportation/transfer within the conductive and intimate 2D heterostructure, the coherent energy flow owing to aligned energy levels, and the enriched electron density at the isolated Ni-N 4 sites boosted by electrostatic charge transfer. [ABSTRACT FROM AUTHOR]