## 1 Introduction  
Gas sensors for household and industrial usages have attracted much attention since 1970 [1]. Toxic gases, such as hydrogen sulfide (H2S), sulfur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO), and nitric oxide (NO), are harmful to plants, organisms, and people's health. Therefore, finding a suitable sensor for toxic gases is an emerging and interesting research field. Experimentally, several key problems and challenges persist in the development of sensing components. For example, the sensor's working or operating temperature may be too high or too low, which restricts its use. The size of the gas-sensing application is also a key factor for a wearable device. Moreover, distinguishing the component and concentration of a specified gas from mixing gases is difficult. The realization of the sensor response to functional or target gases can significantly enhance applications of the biomimetic response and controlling, as well as autonomously release functional gases [2, 3]. The conjugated bimetallopolymer with Pt(II)-acetylide and Ru(II)-porphyrin-pyridyl is polymerized with oligo (phenylene ethynylene) (OPE) backbones and insulated by permethylated \(\alpha\)-cyclodextrintrins (PM \(\alpha\)-CDs) [2]. The conjugated bimetallopolymer is depolymerized by Ru complexes, which behave as acceptors with carbon monoxide (CO) reactivity. The depolymerization of the non-radiative conjugated polymer to luminescent monomers of Pt-acetylide complexes is the first self-activation threshold for the activation of the system. The luminescent intensity increase with the increase in CO concentration is an autonomous response above the threshold. Approaching constant amounts of luminescent Pt-monomers is the second self-regulation threshold for the rate-determining step of the Ru complex. The dual self-controlling system of artificial biomimetic materials can be used as sensors, catalytic systems, and machines transporting materials. The charge-compensating anions HS\({}^{-}\) and NO\({}^{2-}\) and hydrated water (\(m\)H\({}_{2}\)O) in Mg\({}_{y}\)Al(OH)\({}_{2(y+1)}\) (\(y\) is in the range of 2\(\sim\)4) layered double hydroxides (Mg/Al(\(y\)/1) LDHs) are used as the gas release system for medical applications [3]. Interlayer HS\({}^{-}\) and NO\({}^{2-}\) in LDHs are protonated with aerial CO\({}_{2}\) and H\({}_{2}\)O, releasing H\({}_{2}\)S or HNO\({}_{2}\) under air. NO and NO\({}_{2}\) can be further generated through an automatic disproportionation reaction of HNO\({}_{2}\). LDHs (Mg/Al = 2/1 or 3/1) mixed with NaHS, Na\({}_{2}\)S, and NaNO\({}_{2}\), i.e., NaHS-Mg/Al(2/1), NaHS-Mg/Al(3/1), Na\({}_{2}\)S-Mg/Al(2/1), Na\({}_{2}\)S-Mg/Al(3/1), NaNO\({}_{2}\)-Mg/Al(2/1), and NaNO\({}_{2}\)-Mg/Al(3/1) LDHs, have been successfully synthesized to release p.p.m.-level H\({}_{2}\)S and NO derived from aerial CO\({}_{2}\)-stimulated anion exchange, respectively. NaHS-Mg/Al(2/1) and NaNO\({}_{2}\)-Mg/Al(3/1) LDHs showed the best release profile for H\({}_{2}\)S and NO in a rather flat and elongated gas release, respectively. NaNO\({}_{2}\)-Mg/Al(3/1) LDHs have been demonstrated to produce a battery-free respirator for inhaled NO, which is a selective and quick-acting pulmonary vasodilator after inhalation. Metal oxide semiconductors [4], such as SnO\({}_{2}\), Ga\({}_{2}\)O\({}_{3}\), and WO\({}_{3}\) have been widely studied and used as gas sensors [5; 6; 7; 8; 9; 10; 11]. The important features of metal oxide semiconductor sensors are reversible interactions between gas and the surface of metal oxide semiconductors [10]. The SnO\({}_{2}\), Ga\({}_{2}\)O\({}_{3}\), WO\({}_{3}\) and other metal oxide semiconductor sensors can be worked stably at a high temperature from 200 \({}^{\circ}\)C to 900 \({}^{\circ}\)C and can be used for a long time. In recent years, SnO\({}_{2}\), Ga\({}_{2}\)O\({}_{3}\), WO\({}_{3}\), and other sensors have been determined as sensors for detecting CO, H\({}_{2}\), CH\({}_{4}\), O\({}_{3}\), NO\({}_{2}\), H\({}_{2}\)S, SO\({}_{2}\), and other gases [11].