Highly Selective Photosynthesis of Formic Acid by Unifying the Products of CO₂ Reduction and Methanol Oxidation

Photocatalytic conversion of CO 2 to added‐value fuels or chemicals is a promising technology for the effective utilization of the disturbing greenhouse gas, but its economic benefit is limited either by low efficiency due to the difficulty of water oxidation or by the employment of expensive sacrificial reagents. To overcome this dilemma, herein, an effective strategy is reported for the resourceful utilization of CO 2 by creating an eco‐friendly bifunctional photocatalyst to achieve CO 2 photoreduction concurrent with methanol photooxidation to the uniform product of formic acid for the first time. The bifunctional photocatalyst is elaborately constructed by in situ encapsulating lead‐free double perovskite (Cs 2 AgBiBr 6 , abbreviated as CABB) nanocrystals into the pores of Fe‐based metal−organic framework (MIL‐101(Fe)). The tight contact between CABB and MIL‐101(Fe) in the resultant CABB/MIL‐101(Fe) composite facilitates the efficient spatial separation of photogenerated carriers, which leads to the division of reduction and oxidation functional units. CABB/MIL‐101(Fe) composites can unify the redox products into formic acid, reaching an impressive formation yield of 1375 μmol g −1 h −1 with a high selectivity of 97.8%. This work provides a viable strategy for the efficient photosynthesis of formic acid, promoting the cost‐effective utilization of CO 2 .