Coordination‐Encoded Microenvironments in Copper Cluster Metal–Organic Frameworks Govern CO 2 ‐To‐Formate Selectivity Through Intermediate Binding Regulation

ABSTRACT Controlling electrocatalytic selectivity requires more than exposing undercoordinated metal sites; it requires placing reaction intermediates within a binding window that is strong enough for activation yet weak enough for turnover. Here we show that solvent choice can encode this balance directly into copper cluster metal–organic frameworks without changing either the copper precursor or the organic linker. Delivering 1,4‐di(4‐pyridyl)benzene in methanol or N , N ‐dimethylacetamide produces two distinct Cu(I)–thiolate frameworks, Cu 10 dpb and Cu 6 dpb, through coupled cluster growth and reticulation. Cu 10 dpb contains a metal‐dense Cu 3 –Cu 4 –Cu 3 node with short Cu⋯Cu contacts and heterogeneous Cu–S/Cu–O/Cu–N microenvironments, whereas Cu 6 dpb comprises alternating Cu 6 _ 4L and Cu 6 _ 5L nodes built from more uniformly thiolate‐supported Cu 6 S 4 cages. These structural differences reshape adsorption accessibility, CO 2 enrichment and catalytic branching. Cu 10 dpb adsorbs more CO 2 , delivers larger CO 2 ‐dependent currents and reaches a formic‐acid Faradaic efficiency of 49.4% at −1.4 V versus RHE, with a production rate twice that of Cu 6 dpb. In contrast, Cu 6 dpb increasingly favours hydrogen evolution with cathodic bias. Density functional theory reveals the origin of this divergence: The higher‐coordinate Cu 10 surface selectively favours HCOO* over COOH while avoiding deep adsorption wells, whereas lower‐coordinate Cu 6 sites over‐stabilize HCOO, impede product release and bind H* more favourably. Both frameworks retain crystallinity, Cu(I) character and local cluster structure during electrolysis. These findings establish coordination‐tempered adsorption as a design principle for reticular electrocatalysts, linking solvent‐programmed cluster nuclearity to intermediate management and selective carbon conversion. More broadly, this work positions reticular chemistry as a means to programme energy landscapes by constructing, rather than merely supporting, multinuclear active sites.