UC Berkeley

Detecting and removing carbon dioxide from indoor and atmospheric air are among the most important technological challenges of this century. Metal-Organic Frameworks (MOFs), crystalline porous materials built from metal nodes and organic linkers, offer a uniquely tunable platform for both applications because their pore geometry, surface chemistry, and host-guest interactions can be engineered at the molecular level. However, the rational development of MOF-based sensing and capture technologies is limited by a fundamental gap: the macroscopic metrics used to evaluate these technologies (electrical resistance changes, volumetric gas uptake, breakthrough curves) cannot reveal the molecular-level mechanisms that govern performance. This thesis bridges that gap by integrating macroscopic device characterization, atomic-resolution solid-state Nuclear Magnetic Resonance (ssNMR) spectroscopy, and a systems-level analysis of the carbon markets and policy frameworks within which these technologies must ultimately operate.Part I (Chapters 1–5) establishes the amino-functionalized zirconium framework UiO-66-NH₂ as a chemiresistive gas-sensing platform. Interdigitated electrode devices fabricated with UiO-66-NH₂ films demonstrate measurable, reversible responses to CO₂, CH₂O, CO, and CH₄, with preferential sensitivity to polar analytes consistent with specific host-guest interactions within the amine-functionalized pores. A systematic investigation of environmental effects reveals that ambient humidity simultaneously enables charge transport and attenuates the CO₂ response through competitive adsorption, a dual role that macroscopic electrical measurements alone cannot resolve. This unresolved question, what happens at the molecular level when CO₂ enters a MOF pore in the presence of water, motivates the transition to Part II.Part II (Chapters 6–11) deploys multi-nuclear ssNMR spectroscopy (¹H, ¹³C, ¹⁵N, ²⁹Si, ²⁷Al) to investigate the molecular chemistry of CO₂ capture in three structurally distinct MOF systems, each selected to address a different aspect of the CO₂-H₂O-framework interaction. A four-tool analytical framework combining spectral deconvolution, complementary pulse sequences, Density Functional Theory calculations, and comparative analysis is developed and validated through the complete peak assignment of Al-PMOF, a spectrally challenging porphyrin-based framework. This methodology is then applied to the bimetallic Al/Zn PyC MOF (MIP-212), where ssNMR reveals that the two C–N carbons in each pyrazolate ring are chemically inequivalent, one facing into the aluminum-rich pore and the other into the zinc-rich pore, a feature invisible to X-ray diffraction. Systematic gas-dosing experiments establish a partitioned-pathways mechanism: CO₂ and H₂O adsorb preferentially into chemically distinct pore environments, achieving humidity-tolerant physisorption through spatial segregation. The amine-functionalized MOF-808-APTES is then characterized under dry and humid CO₂ conditions, revealing five coexisting CO₂ populations, two physisorbed and three chemisorbed (ammonium carbamate, carbamic acid, and node-associated bicarbonate). The critical finding is that water does not suppress the amine-CO₂ chemistry but instead cooperatively reorganizes the hydrogen-bond network, selectively stabilizing certain binding motifs while preserving others. These two paradigms, passive architectural segregation and active chemical cooperation, represent fundamentally different molecular strategies for humidity tolerance, each with distinct implications for material design.Part III (Chapters 12–14) contextualizes these scientific advances within the broader landscape of carbon dioxide removal (CDR) policy and emerging carbon markets. A systematic analysis of CDR technologies, carbon credit integrity frameworks, and the financial architecture of carbon removal establishes the market conditions under which MOF-based direct air capture must compete. The thesis demonstrates that the molecular-level characterization capabilities developed in Part II, the ability to verify capture mechanisms, quantify sorbent stability, and confirm humidity tolerance at the atomic scale, are not only a scientific contribution but an essential component of the measurement, reporting, and verification infrastructure that a credible, gigatonne-scale carbon removal industry demands.