We report a unique 2D bismuth metal-organic framework (Bi-MOF) that possesses permanent accessible porosity for efficient electrochemical CO₂ reduction (ECR) to HCOOH. The 2D open-framework structure with helical Bi-O rods bridged by tritopic carboxylate ligands exhibits a remarkable Faradaic efficiency for HCOOH formation over a broad potential window, reaching 92.2 % at ∼ –0.9 V (vs. reversible hydrogen electrode, RHE) with excellent durability over 30 h. The mass-specific HCOOH partial current density is up to 41.0 mA mg_Bi⁻¹, exceeding 4 times higher than that of commercial Bi₂O₃ and Bi sheets at ∼ –1.1 V (vs. RHE). Operando and ex-situ X-ray absorption fine structure spectroscopy revealed a structural feature associated with Bi-MOF to preserve Bi(3+) during and after long-term ECR. Theoretical calculations further showed that the crystallographically channels with abundant Bi active sites in the MOF structure favor the formation of *HCOO while suppressing the side-reaction of hydrogen evolution, thereby leading to the high selectivity for HCOOH.

我们报告了一种独特的二维铋金属有机骨架（Bi-MOF），该骨架具有永久可访问的孔隙率，可将HCOOH有效地电化学还原CO ₂（ECR）。具有三位羧酸盐配体桥接的螺旋Bi-O杆的2D开放框架结构在很宽的电位范围内对HCOOH的形成显示出显着的法拉第效率，在〜-0.9 V时达到92.2％（与可逆氢电极RHE相比），具有出色的超过30小时的耐久性。质量比HCOOH分电流密度高达41.0 mA mg _Bi ^-1，在〜–1.1 V时（相对于RHE），比市售Bi ₂ O ₃和Bi薄片高4倍以上。Operando和异地X射线吸收精细结构光谱显示了与Bi-MOF相关的结构特征，可在长期ECR期间和之后保留Bi（3+）。理论计算进一步表明，MOF结构中具有丰富的Bi活性位点的晶体学通道有利于* HCOO的形成，同时抑制了氢逸出的副反应，从而导致了对HCOOH的高选择性。