Novel layer-to-layer charge transfer in an anion-pillared metal-organic framework for efficient CO2 photoreduction to CH4.

[Display omitted] • The incorporation of SiF 6 2− anion-pillars enhances CO 2 adsorption. • CuSiF 6 -TPPY reduces the energy barrier for *CO-to-*CHO while inhibiting desorption of CO. • Layer-to-layer model for photoinduced charge transfer suppresses electron-hole recombination. • Remarkable CH 4 yield of 13.84 μmol g−1 h−1 with a high selectivity of 88.78 %. The highly selective photoreduction of CO 2 to CH 4 is hindered by the sluggish eight-electron transfer process and rapid recombination of charge carriers. Herein, an anion-pillared metal–organic framework photocatalyst, CuSiF 6 -TPPY, is judiciously constructed for the highly selective photoreduction of CO 2 to CH 4. The polar SiF 6 2− pillars significantly enhance the CO 2 adsorption capacity to 96.56 cm3 g−1. Furthermore, the incorporation of SiF 6 2− pillars separates the HOMO and LUMO energy levels in distinct MOF layers, leading to a lower energy barrier for *CHO generation and a higher energy barrier for CO desorption. As a result, CuSiF 6 -TPPY delivers a CH 4 generation rate of 13.84 μmol g−1 h−1 with a high selectivity of 88.78 %, 4-times higher than TPPY ligands. Moreover, in-situ IR spectra and computational simulations further confirm the photoreduction pathways. [ABSTRACT FROM AUTHOR]