Covalent organic frameworks (COFs), a fast-growing field in crystalline porous materials, have achieved tremendous success in structure development and application exploration over the past decade. The vast majority of COFs reported to date are designed according to the basic concept of reticular chemistry, which is rooted in the idea that building blocks are fully connected within the frameworks. We demonstrate here that sub-stoichiometric construction of 2D/3D COFs can be accomplished by the condensation of a hexagonal linker with 4-connected building units. It is worth noting that the partially connected frameworks were successfully reticulated for 3D COFs for the first time, representing the highest BET surface area among imine-linked 3D COFs to data. The unreacted benzaldehydes in COF frameworks can enhance C 2 H 2 and CO 2 adsorption capacity and selectivities between C 2 H 2 /CH 4 and C 2 H 2 /CO 2 for sub-stoichiometric 2D COFs, while the reserved benzaldehydes control the interpenetrated architectures for the 3D case, achieving a rare non-interpenetrated pts topology for 3D COFs. This work not only paves a new avenue to build new COFs and endows residual function groups with further applications but also prompts redetermination of reticular frameworks in highly connected and symmetrical COFs.

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TiC-high Mn steel-bonded carbide with a cellular structure was designed and fabricated by powder metallurgy techniques using coarse and fine TiC particles as the hard phase. This preparation process of the alloy was designed carefully and optimized. The microstructure of the alloy was observed using a scanning electron microscope. The results show that there are two types of microstructures observed in this TiC steel-bonded carbide: the coarse-grained TiC structure and fine-grained TiC structure. The transverse rupture strength and impact toughness of the alloy reach maximum values 2231 MPa and 12.87 J/cm2, respectively, when the starting weight ratio of MP-A (containing coarse TiC particles) to MP-B (containing fine TiC particles) is 60:40. Hence, this study serves as a feasible and economical example to prepare a high-strength and high-toughness TiC-high Mn steel-bonded carbide with little production cost increase.

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The effects of one-step aging and double aging on the properties and microstructures of 7075 Al sheets were studied via mechanical property testing, scanning electron microscopy, and transmission electron microscopy. The results indicated that with continued one-step aging, the tensile and yield strengths of the Al sheets first increased rapidly with an increase in the treatment time to 8 h and then increased slightly with a further increase in the treatment time to 10 h. The tensile and yield strengths became constant after 16 h of treatment. The mechanical strength properties of the Al sheets peaked after 16 h of one-step aging. However, the double aging treatment provided better mechanical properties and working efficiency than the one-step aging treatment. The tensile strength and microhardness resulting from double aging were greater than those resulting from one-step aging by 5.87% and 8.71%, respectively. Herein, we quantified the contribution ofvarious strengthening mechanisms.