Significance The diamond nanothread is predicted to have comparable or larger strength and stiffness than the carbon nanotube but severely suffers from intrathread bonding disorder in practice. Here, we synthesized a bulk crystalline diamond nanothread material C 3 N 3 H 3 with a C/N-ordered tube (3,0) structure via high-pressure topochemical polymerization of s -triazine. The π-stacked s -triazine experienced a selective concerted bonding of three neighbored C···N pairs, completely different from the classical Diels–Alder reactions of aromatics under high pressure. This study obtained the structure-specific diamond nanothread with an unambiguous elemental reaction, which is the basis to realize the expected excellent properties of diamond nanothreads. Following the identified reaction selectivity under high pressure, more structure-specific carbon materials can be designed.

Under pressure of 1–100 GPa, unsaturated organic molecules tend to form covalent bond to each other for a negative enthalpy change, which often produces polymeric materials with extended carbon skeleton. The polymerization reactions typically happen in crystal, which promotes the topochemical process. This review summarized the topochemical polymerization processes of several alkynes, aromatics, and alkynylphenyl compounds, including the critical crystal structures before the reaction, bonding process, and the structure of the products. Secondly, this review also summarized the condensation reaction identified in the polymerization process, including the elimination of small molecules such as NH3, etc.

Purpose The purpose of this paper is to estimate the returns to rural schooling in China, addressing both endogeneity in rural individuals’ schooling and self-selection into off-farm work. Design/methodology/approach This paper exploits geographical proximity to rural secondary schools to create instrumental variables (IV) for individuals’ years of schooling. It addresses both endogenous schooling and self-selection using the two-step procedure developed in Wooldridge (2002, p. 586). Findings The preferred IV estimate of schooling returns, 7.6 percent, is considerably higher than most previous estimates found in rural China. Originality/value This paper is among the few papers that examine returns to rural schooling in China while simultaneously addressing both endogeneity in individuals’ schooling and self-selection into off-farm work. Its findings suggest that rural education in China is potentially able to generate a respectable level of economic returns if policies are designed to provide greater school accessibility to rural individuals.

The four-membered nitrogen ring (N4-ring) is predicted to be a high-energy density moiety and has been the target of chemical synthesis for quite a long time. Here, by compressing the 1:1 co-crystal of trans-azobenzene and trans-perfluoroazobenzene up to ∼40 GPa, the azo groups were restrained closely in parallel in the crystal and underwent two competitive addition reactions. One is [4 + 2] cycloaddition with the azo group as a part of diene and phenyl as dienophile. The other is [2 + 2] cycloaddition between two azo groups, which produced an unprecedented N4-ring structure as evidenced by the metathesis product. The content of the N4-ring structure significantly increases under higher pressure, and we found that it was the external pressure that decreased the kinetic barrier and realized such a high-tensile moiety. Our work shows that high pressure is an alternative synthetic strategy for these high-tensile structures, which can be very effective under the cooperation of crystal engineering.

Pressure-induced topochemical polymerization of molecular crystals with various stackings is a promising way to synthesize materials with different co-existing sub-structures. Here, by compressing the azobenzene crystal containing two kinds of intermolecular stacking, we synthesized an ordered van der Waals carbon nanoribbon (CNR) heterostructure in one step. Azobenzene polymerizes via a [4 + 2] hetero-Diels–Alder (HDA) reaction of phenylazo-phenyl in layer A and a para-polymerization reaction of phenyl in layer B at 18 GPa, as evidenced by in situ Raman and IR spectroscopies, X-ray diffraction, as well as gas chromatography–mass spectrometry and the solid-state nuclear magnetic resonance of the recovered products. The theoretical calculation shows that the obtained CNR heterostructure has a type II (staggered) band gap alignment. Our work highlights a high-pressure strategy to synthesize bulk CNR heterostructures.