CAREER: Catalytic Membranes for Integrated CO2 Capture and Conversion

从空气中捕获二氧化碳（CO2）被认为是减缓全球变暖的重要负排放技术。目前基于吸附剂的二氧化碳捕获工艺非常昂贵，因为吸附剂必须通过一个能量密集的步骤来再生，以释放捕获的二氧化碳。一旦从吸附剂中释放出来，捕获的二氧化碳还必须被压缩并运输到储存地点，这进一步降低了效率。理想的二氧化碳捕获技术应该是高容量和高能效的，同时将废弃的二氧化碳流转化为增值产品。该项目将推进利用新设想的双功能催化膜在单个单元过程中整合二氧化碳捕获和二氧化碳转化的基础科学。膜将作为二氧化碳的分离和转化介质，提供了一种能源和原子效率的替代品，以吸附为基础的二氧化碳捕获、压缩、运输和储存。这种膜可以彻底改变燃料和化学品的生产方式，导致化学加工工业的革命性变化，并长期刺激美国经济。该项目支持的学生将接受催化、膜分离和高级光谱表征方面的跨学科培训。该CAREER项目还将通过在印第安纳州南本德的纳瓦拉中学开展外展活动，以及为来自波多黎各的本科生和研究生提供研究机会，扩大代表性不足群体对STEM的参与。这个CAREER项目旨在推进二氧化碳捕获和转化的基础科学整合到一个单一的、基于膜的过程中。设想的双功能CO2捕获和转化膜是基于聚合物的，具有：(1)胺基团附着在聚合物链上，选择性地捕获来自空气或集中点源的CO2，并促进CO2跨膜运输；(2)催化基团（如胺、卤化物、金属）在膜的渗透侧催化CO2的转化。该项目的研究目标是确定限制二氧化碳捕获和转化总体速率的关键因素（质量传输、反应动力学和稳定性）。该项目将检验环碳酸盐合成作为二氧化碳转化反应的模型。速率限制因素的知识将用于制定规避这些性能限制过程的策略。该项目的创新之处在于，它使用了由研究者开发的独特的operando光谱技术来探测催化膜在实际操作条件下的结构、性能和动力学。研究成果将提供动力学、机制和催化膜稳定性的基础知识，这将为开发一个实用的膜系统提供框架，该系统将二氧化碳捕获与二氧化碳转化为广泛的燃料和化学品。该研究还将推进最先进的operando膜表征，增强CO2分离膜，并增强CO2转化催化剂。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Carbon dioxide (CO2) capture from air is considered an important negative emissions technology to mitigate global warming. Current sorbent-based CO2 capture processes are prohibitively expensive because the sorbent must be regenerated via an energy-intensive step to release the captured CO2. Once released from the sorbent, the captured CO2 must also be compressed and transported to sites for storage, which further reduces efficiency. An ideal CO2 capture technology would be both high-capacity and energy-efficient, while simultaneously converting the waste CO2 stream into a value-added product. This project will advance the fundamental science of integrating CO2 capture with CO2 conversion in a single unit process using a newly-envisioned bifunctional catalytic membrane. The membrane would act as both the CO2 separation and conversion medium, providing an energy- and atom-efficient alternative to sorbent-based CO2 capture, compression, transport, and storage. Such a membrane could revolutionize the way fuels and chemicals are produced, leading to transformative change in the chemical process industries and long-term stimulation of the United States economy. The students supported by this project will receive interdisciplinary training in catalysis, membrane separations, and advanced spectroscopic characterization. This CAREER project will also broaden the participation of underrepresented groups in STEM through outreach activities at Navarre Middle School in South Bend, Indiana, and research opportunities for undergraduate and graduate students from Puerto Rico.This CAREER project aims to advance the fundamental science underlying the integration of CO2 capture and conversion into a single unit, membrane-based process. The envisioned bifunctional CO2 capture and conversion membrane is polymer-based with: (1) amine groups attached to the polymer chain to selectively capture CO2 from air, or concentrated point sources, and facilitate CO2 transport across the membrane; and (2) catalytic groups (e.g. amines, halides, metals) to catalyze conversion of CO2 on the permeate side of the membrane. The research goal of this project is to identify the key factors (mass transport, reaction kinetics, and stability) that limit the overall rate of integrated CO2 capture and conversion. The project will examine cyclic carbonate synthesis as a model CO2 conversion reaction. Knowledge of the rate-limiting factors will be used to develop strategies for circumventing these performance-limiting processes. The project is innovative in its use of unique operando spectroscopy techniques developed by the investigator to probe the structure, performance, and dynamics of the catalytic membranes under realistic operating conditions. The research outcomes will provide foundational knowledge of the kinetics, mechanisms, and stability of the catalytic membrane, which will provide a framework for developing a practical membrane system for integrating CO2 capture with CO2 conversion to a wide range of fuels and chemicals. The research will also advance the state-of-the-art of operando membrane characterization, enhance membranes for CO2 separation, and enhance catalysts for CO2 conversion.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.