Controllable preparation of Cu2O/Cu-CuTCPP MOF heterojunction for enhanced electrocatalytic CO2 reduction to C2H4

[Display omitted] •Cu2O/Cu-CuTCPP MOF is controllably synthesized via an electrodeposition method.•Cu-based electrocatalysts with three Cu sites are firstly constructed for CO2RR.•Compared to Cu-MOF, 1.9-times FEC2H4 (61.8 %) and 2.91-times jC2H4 are achieved.•Formation of Cu2+–O–Cu+–O bond between Cu2O and Cu-MOF is proved a key for C2H4.•Synergic catalysis limits H2, HCOOH and CH4 products, and promotes C2H4 product. Copper-based metal-organic framework (Cu-MOF) materials with multiple active sites have attracted increasing attention to the electrocatalytic CO2 reduction reaction (ECR), however, face the huge challenge owing to the poor stability and low C2 selectivity. Here, the Cu2O/Cu-CuTCPP heterojunction (Cu2O/CPFs) with three Cu active sites are firstly constructed through in-situ electrodeposition method. The effect of CuSO4 concentration and electrodeposition conditions on ECR is systematically investigated. The optimized Cu2O/CPFs composite achieves the ethylene Faraday efficiency (FEC2H4) of 61.8 % at –1.3 V vs. RHE, which is 1.9 and 3.42 times higher than those of CPFs and Cu2O, respectively. Meanwhile, the C2H4 partial current density (jC2H4) of –7.96 mA·cm−2 is 2.91 and 4.68 times higher than those of CPFs and Cu2O. Further experiments reveals that the formation of Cu2+–O–Cu+–O bond between Cu2O and Cu–O4 sites in Cu2O/CPF heterojunction is crucial. Consequently, the hydrogen (H2), formic acid (HCOOH) and methane (CH4) evolution reactions are restricted, the C–C coupling reaction of *CHO and *CO intermediates is significantly enhanced, and the Cu–O4 sites in CPFs are protected. This work provides an effective strategy to stabilize MOF structure and obtain high value-added C2+ products.