The construction industry promotes the economic development of the country by addressing society’s housing needs. However, the industry’s energy consumption and carbon dioxide (CO2) emissions are the primary contributors to global warming. Traditional building materials are no longer capable of meeting the requirements of sustainable development, while natural cellulose can be used as a new type of carbon capture construction material. Inspired by the “reinforced concrete” methodology, a mineralized cellulose composite (ML-CCM) was fabricated through a strategy of vacuum filling and in-situ mineralization, resulting in a composite with a multilevel structure (a natural microporous 3D scaffold loofah as “rebar” and cellulose filler as “cement” are staggered in the composite). The resultant ML-CCM1 exhibited a significantly high flexural strain (approximately 215.9 % of that of cellulose composite without loofah) because of the 3D scaffold loofah acting as a “rebar”. Furthermore, the composite possesses flame retardancy, superior thermal insulation at 90 ?C, and passive radiative cooling performance due to the micro-nano ZnO particle in the “cement”. Moreover, the multi-level structure, consisting of pores and micro-nano particles, enables it to effectively adsorb CO2 and environment tobacco smoke. As a result, lifecycle assessments underscore the composite’s low Global Warming Potential. Therefore, this work reports a promising 3D bio-based composite with CO2 capture for energy conservation and carbon reduction in the construction industry.