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This paper introduces a novel crystallization-enabled proton management strategy to control electronic states in conductive metal-organic frameworks (c-MOFs) without altering their fundamental structure or requiring post-synthetic doping. By manipulating the proton environment during the assembly of Co9HHTP4 using HNO3, the researchers achieved a significant enhancement in electron retention and conductivity, reaching 8.4 * 10-2 S cm-1, a four-order-of-magnitude improvement over the NaOAc-crystallized counterpart. This work establishes crystallization conditions as a tunable parameter for programming charge transport in c-MOFs, offering a new avenue for designing advanced electronic materials.
Crystallization conditions, not just framework composition, can program the electronic states and conductivity of c-MOFs, yielding a four-order-of-magnitude conductivity jump in Co9HHTP4.
Conductive metal-organic frameworks (c-MOFs) are promising electronic materials, where electronic states critically determine electrical conductivity. However, achieving controllable modulation of these states during crystallization remains challenging. Existing approaches rely either on redesigning framework components or on introducing external dopants after crystallization, making electronic-state regulation dependent on structural modification or postsynthetic doping. Here, we demonstrate a crystallization-enabled in situ proton-management strategy for regulating the electronic state of c-MOFs. Using Co9HHTP4 as a model system, we show that distinct proton environments influence the balance between competing proton-coupled electron-transfer pathways during Co-O framework assembly while preserving the fundamental framework architecture. HNO3-mediated crystallization produces an electronic state consistent with enhanced electron retention within the Co-O framework and results in a single-crystal conductivity of 8.4 * 10-2 S cm-1, nearly four orders of magnitude higher than Co9HHTP4-NaOAc (1.7 * 10-5 S cm-1), together with a substantially reduced transport activation energy. Hall measurements further reveal a pronounced increase in carrier concentration for Co9HHTP4-HNO3, providing direct evidence that the enhanced conductivity is associated with a substantially increased carrier population. These results establish crystallization conditions as an active parameter for programming electronic states and charge transport in conductive frameworks.
