Disentangling the efficient photocatalytic reduction of CO2 by a stable UiO-66-NH2/Cs2AgBiBr6 catalyst

The compelling global warming crisis as well as extraterrestrial artificial light synthesis craves photocatalytic reduction of CO into fuels and value-added chemicals, for which efficient and robust catalysts with high selectivity and conversion rate is a prerequisite but hitherto a rarity. Herein we create a lead-free double metal perovskite of CsAgBiBr, coupling with mesoporous/microporous UiO-66-NH MOF to form type-II heterojunctions for efficient photocatalytic reduction of CO with a high CO selectivity of 95 % at an electron consumption rate of 33 μmol g h (13.4 μmol g h for CO and 0.72 μmol g h for CH). Multilayered mesoporous MOF particles manifest higher catalytic activity than their microporous counterparts due to the highly open mesoporous channels and larger pore volume of the former. Femtosecond transient absorption in combination with in situ infrared spectroscopic measurements disentangle the underlying mechanism accounting for the high product selectivity: the ultrafast electron transfer of 12.3 ps from CsAgBiBr to UiO-66-NH-2 enables efficient charge separation; primary *COOH intermediates and rapid CO desorption from Bi-based photocatalyst lead to dominant CO product. Moreover, the MOF crystals maintain stability after γ-rays irradiation equivalent of over 45-year accumulation in a typical earth orbit, hinting their promising potential in extraterrestrial artificial light synthesis.