Metal-organic frameworks (MOFs) are well-known porous materials owing to their useful adsorption properties; however, some MOFs have limited adsorption capabilities, which can significantly undermine their success as porous materials. Therefore, maximizing their porosity is critical for unlocking their full potential and expanding their practical utilization, such as gas storage, separation, and removal. In this study, flexible MOFs with defined defects were synthesized using a ligand-mixing strategy to improve their porosity and maximize their adsorption capacities. Specifically, we employed a combination of two organic linkers, 4,4'-biphenyldicarboxylic acid (H₂BPDC) and 1,4-benzenedicarboxylic acid (H₂BDC), in various ratios, to fabricate flexible In-MIL-53D hybrids containing controllable defects within the structure due to the incorporation of the short linker (H₂BDC) compared to the original linker (H₂BPDC). These structural defects in the In-MIL-53D hybrids activated their gate-openings and enhanced gas adsorption capacities for N₂ and CO₂. Moreover, the gate-opened activated hybrids exhibited excellent adsorption capacity for the harmful chemical warfare agent simulant, 2-chloroethyl ethyl sulfide (CEES). However, excessive incorporation of defects disrupted the framework's integrity, compromising its stability and increasing the risk of collapse. Therefore, achieving an optimal level of defect incorporation is essential to balance structural stability with enhanced functionality. Among the hybrids, the sample with approximately 39% incorporation of the short linker exhibited up to an 11-fold increase in adsorption capacity for CO₂ at 1 <i>P</i>/<i>P</i>₀. In addition, this hybrid demonstrated up to 5-fold higher CEES adsorption capacity compared to the pristine In-MIL-53D, highlighting its potential for advanced utilization in relevant fields.

ConspectusOverflowing metal-organic frameworks (MOFs) have been synthesized from a wide range of metal and organic components for specific purposes and intellectual curiosity. Each MOF has unique chemical and structural characteristics directed by the incorporated components, metal ions (or clusters), organic linkers, and their intrinsic coordination interactions. These incorporated components and structural characteristics are two pivotal factors influencing MOFs' fundamental properties and subsequent applications. Therefore, selecting the appropriate metal and organic components, considering their innate chemical and structural properties, is crucial to endow the final MOFs with the desired properties. Ultimately, producing MOFs with a desired structure using ideal components is the best approach to achieving the best MOFs tailored for specific purposes with desired properties. However, achieving MOFs with the intended structure from chosen components remains underdeveloped. In many cases, the resulting MOF structure is governed by the thermodynamically and/or kinetically preferred configuration (refers to a naturally preferred structure) of the chosen components and given reaction conditions. Additionally, producing hybrid MOFs with complex components, structures, and morphologies presents a great opportunity to obtain special MOFs with advanced properties and functions. In this Account, we outline our group's efforts over the past few years to develop naturally nonpreferred MOFs through the induced MOF-on-MOF growth process and atypical hybrid MOFs via nonstandard MOF-on-MOF growth. First, we highlight the prime strategy for producing naturally nonpreferred MOFs based on template-induced MOF-on-MOF growth. In this section, we discuss the two basic growth behaviors, isotropic and anisotropic growth of naturally nonpreferred MOFs, determined by the degree of matching between the cell lattices of the two MOFs. Second, we introduce the MOF farming concept for the productive cultivation and effective harvesting of naturally nonpreferred MOFs made by MOF-on-MOF growth. Here we discuss the importance of selecting the ideal MOF template for productive growth and developing an efficient method for harvesting cultivated MOFs. Next, we describe atypical anisotropic MOF-on-MOF growths between two MOFs with mismatched cell lattices. In this section, we introduce tip-to-middle MOF-on-MOF growth involving self-structural adjustment of the secondary MOF, logical inference of unidentified MOF structures based on MOF-on-MOF growth behavior and morphological features, and MOF-on-MOF growth accompanied by etching and transformation of the template. Finally, we discuss the perspectives and challenges of MOF-on-MOF growth and the synthesis of naturally nonpreferred MOFs. We hope that this Account offers valuable insights into the rational design and development of MOFs with desired structural and compositional characteristics, leading to the creation of ideal MOFs.