Patent Description:
Hitherto, as disclosed in NPL <NUM>, an adsorption heat pump that uses carbon dioxide as refrigerant and uses spherical activated carbon as an adsorbent is known. <CIT> discloses an adsorption heat pump that uses a fluid mixture which is a gaseous mixture, with the adsorbable component being carbon dioxide, water vapor, steam, fluorinated hydrocarbon, sulphur dioxide or ammonia. The adsorbent beds are particles of silica gel, natural zeolites and synthetic zeolites.

A process for producing spherical activated carbon is complex; therefore, an adsorbent that has an effective adsorption amount larger than or equal to that of spherical activated carbon and that is easily produced is desired.

An adsorption heat pump according to the present invention is defined in claim <NUM>. It uses, as refrigerant, carbon dioxide and uses, as an adsorbent, a metal-organic framework including a metal ion and one or a plurality of organic ligands. At least one of the organic ligands is represented by
<CHM>
(in the formula, R<NUM> to R<NUM> are each independently selected from an alkyl group, an aryl group, an alkoxyl group, an alkene, an alkyne, a phenyl group, a substituted group thereof, a sulfur-containing group, a silicon-containing group, a nitrogen-containing group, an oxygen-containing group, a halogen, a nitro, an amino, a cyano, a boron-containing group, a phosphorus-containing group, a carboxylic acid, an ester, H, NH<NUM>, CN, OH, =O, =S, Cl, I, F,
<CHM>
<CHM>
<CHM>
<CHM>
(in the formulae, x is <NUM>, <NUM>, or <NUM>),.

The adsorption heat pump according to the first aspect uses an adsorbent that has a high effective adsorption amount and that is easily produced.

An adsorption heat pump according to a second aspect is the adsorption heat pump according to the first aspect, in which the metal-organic framework is MOF-<NUM>.

The adsorption heat pump according to the second aspect uses an adsorbent that has a high effective adsorption amount and that is easily produced.

An adsorption heat pump according to a third aspect is the adsorption heat pump according to the first aspect or the second aspect, in which a refrigeration cycle is performed such that a temperature and a pressure of the refrigerant at a time of high pressure are lower than critical points.

The adsorption heat pump according to the third aspect uses an adsorbent that has a high effective adsorption amount and that is easily produced.

An adsorption heat pump according to a fourth aspect is the adsorption heat pump according to the first aspect or the second aspect, in which a refrigeration cycle is performed such that one of a temperature and a pressure of the refrigerant at a time of high pressure is lower than a critical point.

The adsorption heat pump according to the fourth aspect uses an adsorbent that has a high effective adsorption amount and that is easily produced.

An adsorption heat pump <NUM> according to an embodiment of the present disclosure will be described with reference to the drawings.

The adsorption heat pump <NUM> is a device that uses the transfer of latent heat generated when refrigerant adsorbs to an adsorbent and when refrigerant desorbs from an adsorbent to generate cooling energy from a heat source at a relatively low temperature of <NUM> to <NUM>.

As illustrated in <FIG> and <FIG>, the adsorption heat pump <NUM> mainly includes an evaporator <NUM>, a condenser <NUM>, a first adsorber <NUM>, and a second adsorber <NUM>. The evaporator <NUM> and the first adsorber <NUM> are connected by a first flow path <NUM>. The evaporator <NUM> and the second adsorber <NUM> are connected by a second flow path <NUM>. The condenser <NUM> and the first adsorber <NUM> are connected by a third flow path <NUM>. The condenser <NUM> and the second adsorber <NUM> are connected by a fourth flow path <NUM>. The evaporator <NUM> and the condenser <NUM> are connected by a fifth flow path <NUM>. The first flow path <NUM> to the fourth flow path <NUM> are provided with a first valve <NUM> to a fourth valve <NUM> for opening and closing the flow paths, respectively.

The evaporator <NUM> evaporates liquid refrigerant to generate gas refrigerant. The condenser <NUM> condenses gas refrigerant to generate liquid refrigerant. The first adsorber <NUM> and the second adsorber <NUM> have an adsorbent <NUM> for adsorbing and desorbing refrigerant. The adsorbent <NUM> is a substance whose adsorption amount of refrigerant changes depending on the pressure and the temperature. In this embodiment, the refrigerant is carbon dioxide, and the adsorbent <NUM> is MOF-<NUM>, which is a metal-organic framework (MOF). The mass of the adsorbent <NUM> in the first adsorber <NUM> is equal to the mass of the adsorbent <NUM> of the second adsorber <NUM>.

The evaporator <NUM> is a heat exchanger for extracting cooling energy. A first pipe <NUM> is arranged inside the evaporator <NUM>. The first pipe <NUM> is a pipe through which a heat transfer medium flows, the heat transfer medium being a medium for transferring, to the outside, cooling energy generated when liquid refrigerant evaporates inside the evaporator <NUM>. The heat transfer medium flowing inside the first pipe <NUM> is, for example, water. In <FIG>, gas refrigerant is adsorbed by the adsorbent <NUM> in the first adsorber <NUM>, and gas refrigerant thereby flows from the evaporator <NUM> into the first adsorber <NUM> through the first flow path <NUM>. In <FIG>, gas refrigerant is adsorbed by the adsorbent <NUM> in the second adsorber <NUM>, and gas refrigerant thereby flows from the evaporator <NUM> into the second adsorber <NUM> through the second flow path <NUM>. When the refrigerant is adsorbed in the first adsorber <NUM> and the second adsorber <NUM>, gas refrigerant flows from the evaporator <NUM>; therefore, evaporation of liquid refrigerant is accelerated in the evaporator <NUM>. The cooling energy generated when liquid refrigerant evaporates, is transferred to the outside by the heat transfer medium flowing inside the first pipe <NUM> and used for, for example, cooling.

The condenser <NUM> is a heat exchanger for condensing gas refrigerant by cooling. A second pipe <NUM> is arranged inside the condenser <NUM>. The second pipe <NUM> is a pipe through which a medium for condensing gas refrigerant inside the condenser <NUM> flows, the medium being a heat transfer medium at a temperature lower than the condensation temperature of the refrigerant or a heat transfer medium at a temperature lower than the temperature of the refrigerant when the refrigerant is in a supercritical state. The heat transfer medium flowing inside the second pipe <NUM> is, for example, water. In <FIG>, gas refrigerant desorbs in the second adsorber <NUM>, and the gas refrigerant flows from the second adsorber <NUM> into the condenser <NUM> through the fourth flow path <NUM>. In <FIG>, gas refrigerant desorbs in the first adsorber <NUM>, and the gas refrigerant flows from the first adsorber <NUM> into the condenser <NUM> through the third flow path <NUM>. Liquid refrigerant generated by condensation of the gas refrigerant in the condenser <NUM> is supplied to the evaporator <NUM> through the fifth flow path <NUM>.

A third pipe <NUM> and a fourth pipe <NUM> are arranged inside the first adsorber <NUM> and the second adsorber <NUM>, respectively. The adsorbent <NUM> is disposed around each of the third pipe <NUM> and the fourth pipe <NUM>. The third pipe <NUM> is a pipe through which a heat transfer medium flows, the heat transfer medium being a medium for controlling the temperature of the adsorbent <NUM> in the first adsorber <NUM>; the fourth pipe <NUM> is a pipe through which a heat transfer medium flows, the heat transfer medium being a medium for controlling the temperature of the adsorbent <NUM> in the second adsorber <NUM>. The heat transfer media flowing inside the third pipe <NUM> and the fourth pipe <NUM> are, for example, water. By controlling the temperatures of the media flowing through the third pipe <NUM> and the fourth pipe <NUM>, the temperatures of the adsorbents <NUM> are controlled such that adsorption or desorption of the refrigerant is performed in the first adsorber <NUM> and the second adsorber <NUM>.

As illustrated in <FIG>, in an adsorption process of causing the refrigerant to adsorb to the adsorbent <NUM> in the first adsorber <NUM>, a medium at a temperature at which adsorption of the refrigerant occurs dominantly, is caused to flow through the third pipe <NUM>. As illustrated in <FIG>, in a desorption process of causing the refrigerant to desorb from the adsorbent <NUM> in the second adsorber <NUM>, a medium at a temperature at which desorption of the refrigerant occurs dominantly, is caused to flow through the fourth pipe <NUM>. For example, in <FIG>, cold water for cooling the adsorbent <NUM> in the first adsorber <NUM>, flows through the third pipe <NUM>, and hot water for heating the adsorbent <NUM> in the second adsorber <NUM>, flows through the fourth pipe <NUM>.

As illustrated in <FIG>, in an adsorption process of causing the refrigerant to adsorb to the adsorbent <NUM> in the second adsorber <NUM>, a medium at a temperature at which adsorption of the refrigerant occurs dominantly, is caused to flow through the fourth pipe <NUM>. As illustrated in <FIG>, in a desorption process of causing the refrigerant to desorb from the adsorbent <NUM> in the first adsorber <NUM>, a medium at a temperature at which desorption of the refrigerant occurs dominantly, is caused to flow through the third pipe <NUM>. For example, in <FIG>, cold water for cooling the adsorbent <NUM> in the second adsorber <NUM>, flows through the fourth pipe <NUM>, and hot water for heating the adsorbent <NUM> in the first adsorber <NUM>, flows through the third pipe <NUM>.

The adsorption heat pump <NUM> switches the open-closed states of the first valve <NUM> to the fourth valve <NUM> to repeat the adsorption processes and the desorption processes, and thus can continuously generate cooling energy from heating energy. Specifically, the adsorption heat pump <NUM> alternately switches a first open-closed state illustrated in <FIG> and a second open-closed state illustrated in <FIG>. In the first open-closed state, the first valve <NUM> and the fourth valve <NUM> are in the open state, and the second valve <NUM> and the third valve <NUM> are in the closed state. In the second open-closed state, the first valve <NUM> and the fourth valve <NUM> are in the closed state, and the second valve <NUM> and the third valve <NUM> are in the open state.

In the first open-closed state, the first adsorber <NUM> is connected to the evaporator <NUM>, and the second adsorber <NUM> is connected to the condenser <NUM>. In the first adsorber <NUM>, the adsorbent <NUM> is cooled by causing cold water or the like to flow through the third pipe <NUM>. In the second adsorber <NUM>, the adsorbent <NUM> is heated by causing hot water or the like to flow through the fourth pipe <NUM>. Thus, the refrigerant supplied from the evaporator <NUM> adsorbs to the adsorbent <NUM> in the first adsorber <NUM>, and the refrigerant desorbs from the adsorbent <NUM> in the second adsorber <NUM> and is supplied to the condenser <NUM>.

In the second open-closed state, the second adsorber <NUM> is connected to the evaporator <NUM>, and the first adsorber <NUM> is connected to the condenser <NUM>. In the second adsorber <NUM>, the adsorbent <NUM> is cooled by causing cold water or the like to flow through the fourth pipe <NUM>. In the first adsorber <NUM>, the adsorbent <NUM> is heated by causing hot water or the like to flow through the third pipe <NUM>. Thus, the refrigerant supplied from the evaporator <NUM> adsorbs to the adsorbent <NUM> in the second adsorber <NUM>, and the refrigerant desorbs from the adsorbent <NUM> in the first adsorber <NUM> and is supplied to the condenser <NUM>.

The adsorption heat pump <NUM> alternately switches the first open-closed state and the second open-closed state, and the adsorption process and the desorption process are thereby alternately performed in each of the first adsorber <NUM> and the second adsorber <NUM>. Accordingly, the adsorption heat pump <NUM> can continuously perform adsorption and desorption of the refrigerant and thus can continuously generate cooling energy.

The adsorbent <NUM> disposed inside the first adsorber <NUM> and the second adsorber <NUM> is MOF-<NUM>, which is one of metal-organic frameworks (MOF). Metal-organic frameworks are crystalline compounds in which coordinate bonds between a metal and an organic substance are continuously formed. Metal-organic frameworks are generated by combining a metal ion or an organometallic salt and a crosslinkable organic ligand that binds the metal ion or the organometallic salt. Metal-organic frameworks may include a plurality of types of organic ligands.

Metal-organic frameworks are porous coordination polymers having a large number of voids (pores) therein. Metal-organic frameworks are used as, for example, porous materials having a function of selective storage and separation of molecules and ions. In this embodiment, a metal-organic framework is used as the adsorbent <NUM> for adsorbing and desorbing carbon dioxide serving as refrigerant.

Some of such metal-organic frameworks are called by various abbreviated names such as MOF-<NUM> and MOF-<NUM>. As the surface area (specific surface area) per unit mass of a metal-organic framework increases, the numerical value included in the abbreviated name tends to increase.

A reference literature related to the metal-organic framework MOF-<NUM> is, for example, <NPL>). As described in this reference literature, MOF-<NUM> has a three-dimensional network structure in which an organometallic salt Zn<NUM>O(CO<NUM>)<NUM> is coordinated by an organic ligand <NUM>,<NUM>',<NUM>"-[benzene-<NUM>,<NUM>,<NUM>-triyl-tris(benzene-<NUM>,<NUM>-diyl)]tribenzoate (BBC). The organometallic salt Zn<NUM>O(CO<NUM>)<NUM> has an octahedral structure. The organic ligand BBC has a triangular shape as represented by the following chemical structural formula.

The three-dimensional network structure of MOF-<NUM> is represented by "qom" in the reticular chemistry structure resource (RCSR) database. The qom structure is suitable for decreasing dead volume and increasing gas storage capacity per unit volume.

MOF-<NUM>, which is one of metal-organic frameworks, has the qom structure, which is the same as the structure of MOF-<NUM>. In the case of MOF-<NUM>, the organic ligand is <NUM>,<NUM>',<NUM>"-benzene-<NUM>,<NUM>,<NUM>-triyl-tribenzoate (BTB). The organic ligand BTB is represented by the following chemical structural formula.

Basic physical properties of MOF-<NUM> are as follows.

The metal-organic framework can be synthesized by various methods. A solution method, which is the simplest synthesis method, is a method for generating a metal-organic framework by mixing a metal and an organic ligand in a solution at ordinary temperature and ordinary pressure. In the solution method, the size of crystals generated can be controlled by adjusting the mixing speed. In the case of MOF-<NUM>, a solution of a metal is a solution of the organometallic salt Zn<NUM>O(CO<NUM>)<NUM>. In this embodiment, the metal-organic framework may be synthesized by any method selected from known methods such as a diffusion method, a hydrothermal method, a microwave method, an ultrasonic wave method, and a solid-phase synthesis method besides the solution method.

The performance of the metal-organic framework serving as the adsorbent <NUM> is measured in terms of effective adsorption amount. In the case of the adsorption heat pump <NUM>, the "effective adsorption amount" refers to a mass of refrigerant (carbon dioxide) that can be adsorbed and desorbed by a unit mass (<NUM>) of a metal-organic framework (MOF-<NUM>) in one adsorption cycle. In one adsorption cycle, the first adsorber <NUM> and the second adsorber <NUM> perform the adsorption process once and the desorption process once.

<FIG> is a graph of adsorption isotherm of MOF-<NUM>. <FIG> shows the relation between the pressure (MPa) and the absolute adsorption amount (g/g) of refrigerant (carbon dioxide) at six temperatures. The "absolute adsorption amount" refers to a mass of refrigerant adsorbed by a unit mass (<NUM>) of a metal-organic framework. The absolute adsorption amount can be measured with, for example, a magnetic suspension balance adsorption amount measuring device. As shown in <FIG>, the adsorption isotherm shows different tendencies depending on the temperature.

In <FIG>, an adsorption cycle is shown by a rectangle. In the adsorption cycle, the refrigerant is adsorbed to the adsorbent <NUM> (the adsorbent <NUM> in the first adsorber <NUM> in <FIG>) at the evaporation pressure, and the refrigerant is desorbed from the adsorbent <NUM> (the adsorbent <NUM> in the second adsorber <NUM> in <FIG>) at the condensation pressure. ΔW shown in <FIG> represents the amount of refrigerant newly adsorbed by the adsorbent <NUM> during one adsorption cycle and corresponds to the effective adsorption amount. As shown in <FIG>, in the case of using MOF-<NUM>, the effective adsorption amount of the refrigerant is <NUM>/g. In other words, the adsorption heat pump <NUM> can adsorb and desorb carbon dioxide in a mass determined by multiplying a dry mass of the adsorbent <NUM> in the first adsorber <NUM> or the second adsorber <NUM> by <NUM> in one adsorption cycle.

A capacity Qc of the adsorption heat pump <NUM> is represented by the following formula. <MAT> (In the formula, M represents the dry mass of the adsorbent <NUM>, L represents the evaporation latent heat of the refrigerant, and ΔW represents the effective adsorption amount of the adsorbent <NUM>.

As represented by the above formula, the higher the effective adsorption amount of refrigerant, the higher the capacity Qc of the adsorption heat pump <NUM>. Therefore, an adsorbent <NUM> having a high effective adsorption amount is desired. Metal-organic frameworks are easily generated and enable the production of compounds having various chemical and physical properties depending on the combination of the metal and the organic ligand thereof. Among metal-organic frameworks, MOF-<NUM> has a higher effective adsorption amount of carbon dioxide than other metal-organic frameworks and other porous materials.

As a comparative example, <FIG> shows a graph of adsorption isotherm of MOF-<NUM>. As shown in <FIG>, the metal-organic framework MOF-<NUM> has an effective adsorption amount of <NUM>/g.

As another comparative example, <FIG> shows a graph of adsorption isotherm of MOF-<NUM> (Mg), which is one of metal-organic frameworks. As shown in <FIG>, the metal-organic framework MOF-<NUM> (Mg) has an effective adsorption amount of <NUM>/g.

The spherical activated carbon disclosed in NPL <NUM> has an effective adsorption amount of <NUM>/g. Thus, the metal-organic framework MOF-<NUM> has good performance as an adsorbent compared with MOF-<NUM>, MOF-<NUM> (Mg), and the spherical activated carbon.

Hitherto, as disclosed in NPL <NUM>, an adsorption heat pump <NUM> that uses activated carbon as an adsorbent is known. However, the metal-organic framework used as the adsorbent <NUM> in the adsorption heat pump <NUM> of this embodiment is generated easily and at low cost compared with activated carbon.

In general, the process for producing activated carbon includes a step of crushing a raw material such as coal into granules and performing molding, a step of subsequently subjecting the resulting molded material to dry distillation at a high temperature of <NUM> to <NUM> for a long time to carbonize the molded material, and an activation step of subsequently causing a reaction with water vapor at a high temperature of <NUM> to <NUM>,<NUM> to form pores. In contrast, the process for producing a metal-organic framework includes only mixing solutions of a metal and an organic ligand at ordinary temperature and ordinary pressure, as described above. Furthermore, in the case where the size of pores and the specific surface area are made uniform, the process for producing activated carbon requires an activation step using an alkali solution, resulting in high cost, whereas the process for producing a metal-organic framework does not require any special step. Thus, the adsorption heat pump <NUM> that uses a metal-organic framework as the adsorbent <NUM> is good in terms of production cost.

In addition, various types of metal-organic frameworks can be generated by various combinations of metals and organic ligands. Among metal-organic frameworks, MOF-<NUM> is particularly good in terms of effective adsorption amount of carbon dioxide. With an increase in the effective adsorption amount of substance used as the adsorbent <NUM>, the amount of adsorbent <NUM> used can be reduced, and the cost can be reduced. Accordingly, the adsorption heat pump <NUM> that uses the metal-organic framework MOF-<NUM> as the adsorbent <NUM> is preferred in view of efficiency of the refrigerating capacity and the cost compared with the case where another metal-organic framework such as MOF-<NUM> is used.

Modifications of the above embodiment will be described below. Some or all of the contents of each modification may be combined with the contents of another modification as long as they do not contradict each other.

The configuration of the adsorption heat pump <NUM> is not limited to those illustrated in <FIG> and <FIG>. For example, the adsorption heat pump <NUM> may be provided with dampers that are opened and closed by the atmospheric pressure instead of the first valve <NUM> to the fourth valve <NUM> installed in the first flow path <NUM> to the fourth flow path <NUM>, respectively.

In this modification, for example, dampers that are opened by the pressure of the refrigerant evaporated in the evaporator <NUM> are installed instead of the first valve <NUM> and the second valve <NUM>. A damper that is opened by the pressure of the refrigerant desorbed from the adsorbent <NUM> in the first adsorber <NUM> is installed instead of the third valve <NUM>. A damper that is opened by the pressure of the refrigerant desorbed from the adsorbent <NUM> in the second adsorber <NUM> is installed instead of the fourth valve <NUM>.

In the first open-closed state, the adsorption heat pump <NUM> causes a medium for cooling the adsorbent <NUM> to flow through the third pipe <NUM> in the first adsorber <NUM> and causes a medium for heating the adsorbent <NUM> to flow through the fourth pipe <NUM> in the second adsorber <NUM>. In the second open-closed state, the adsorption heat pump <NUM> causes a medium for heating the adsorbent <NUM> to flow through the third pipe <NUM> in the first adsorber <NUM>, and causes a medium for cooling the adsorbent <NUM> to flow through the fourth pipe <NUM> in the second adsorber <NUM>.

The adsorption heat pump <NUM> needs to have a cooling circuit through which a medium for cooling the adsorbent <NUM> is caused to circulate and a heating circuit through which a medium for heating the adsorbent <NUM> is caused to circulate. The adsorption heat pump <NUM> may have a mechanism capable of switching between the cooling circuit and the heating circuit in accordance with the open-closed state.

The adsorption heat pump <NUM> preferably performs a refrigeration cycle such that, during the rated operation, the temperature and the pressure of the refrigerant at a time of high pressure are lower than critical points. The "refrigerant at a time of high pressure" refers to the refrigerant in a state of the condensation pressure in the adsorption cycle and is specifically the refrigerant within the condenser <NUM>.

<FIG> is a phase diagram of carbon dioxide, which is the refrigerant used in the adsorption heat pump <NUM>. In the case of carbon dioxide, the critical point of the temperature is about <NUM>, and the critical point of the pressure is about <NUM> MPa. When both the temperature and the pressure are higher than or equal to the critical points, carbon dioxide is in a supercritical state in which gas and liquid cannot coexist. Accordingly, the adsorption heat pump <NUM> preferably controls the pressure and the temperature of the refrigerant at the time of high pressure such that both the temperature and the pressure are lower than the critical points.

The adsorption heat pump <NUM> may perform a refrigeration cycle such that, during the rated operation, one of the temperature and the pressure of the refrigerant at the time of high pressure is lower than the critical point. In this modification, the adsorption heat pump <NUM> may control the pressure and the temperature of the refrigerant such that the refrigerant at the time of high pressure is in a subcritical state. The "subcritical state" refers to a state where one of the temperature and the pressure is lower than the critical point. As shown in <FIG>, the subcritical state is usually a state where the temperature is lower than the critical point and the pressure is close to the critical point. In the subcritical state, the pressure may be higher than or equal to the critical point.

As shown in <FIG>, the metal-organic framework MOF-<NUM> has an effective adsorption amount of <NUM>/g. However, the effective adsorption amount of the metal-organic framework MOF-<NUM> is affected by various parameters such as the degrees of uniformity of the size of pores and the specific surface area of MOF-<NUM>. Therefore, the effective adsorption amount of the metal-organic framework MOF-<NUM> may be within a predetermined range. For example, the effective adsorption amount of the metal-organic framework MOF-<NUM> may be within a range of <NUM>/g to <NUM>/g.

The evaporation pressure and the condensation pressure of the adsorption cycle shown in <FIG> may also be within predetermined ranges. For example, in <FIG>, the evaporation pressure may be within a range of <NUM> MPa to <NUM> MPa, and the condensation pressure may be within a range of <NUM> MPa to <NUM> MPa.

The metal-organic framework used in the embodiment is MOF-<NUM>. However, the metal-organic framework is not limited to MOF-<NUM> as long as the effective adsorption amount is within a predetermined range. The predetermined range of the effective adsorption amount is, for example, <NUM>/g to <NUM>/g.

Specifically, the metal-organic framework used in the adsorption heat pump <NUM> may be, for example, a metal-organic framework having at least one organic ligand represented by the following formula. <CHM>
(In the formula, R<NUM> to R<NUM> are each independently selected from an alkyl group, an aryl group, an alkoxyl group, an alkene, an alkyne, a phenyl group, a substituted group thereof, a sulfur-containing group, a silicon-containing group, a nitrogen-containing group, an oxygen-containing group, a halogen, a nitro, an amino, a cyano, a boron-containing group, a phosphorus-containing group, a carboxylic acid, an ester, H, NH<NUM>, CN, OH, =O, =S, Cl, I, F,
<CHM>
<CHM>
<CHM>
<CHM>
(in the formulae, x is <NUM>, <NUM>, or <NUM>),.

The adsorption heat pump <NUM> has the first valve <NUM> to the fourth valve <NUM>. The timings of opening and closing the first valve <NUM> to the fourth valve <NUM> may be appropriately set in accordance with, for example, the evaporation pressure and the condensation pressure of the adsorption cycle, and the amounts of refrigerant in the evaporator <NUM> and the condenser <NUM>.

The adsorption heat pump <NUM> includes the evaporator <NUM> and the condenser <NUM>. When carbon dioxide is used as the refrigerant, the evaporator <NUM> and the condenser <NUM> are preferably, for example, cross-fin tube type heat exchangers.

The adsorption heat pump <NUM> uses, for example, carbon dioxide as the refrigerant. Therefore, the temperature of the heat transfer medium flowing inside the first pipe <NUM> of the evaporator <NUM> becomes below the freezing point. Accordingly, the adsorption heat pump <NUM> can be used as, for example, a refrigerating machine.

An embodiment of the present invention has been described above. It is to be understood that the forms and the details can be changed in various ways. The scope of the present invention is only defined by the appended claims.

Claim 1:
An adsorption heat pump (<NUM>) comprising carbon dioxide as refrigerant and an adsorbent,
wherein a metal-organic framework including a metal ion and one or a plurality of organic ligands is used as the adsorbent (<NUM>), and at least one of the organic ligands is represented by
<CHM>
wherein
R<NUM>-R<NUM> each independently are alkyl, aryl, alkoxyl, alkene, alkyne, phenyl, a substituted group thereof, a sulfur-containing group, a silicon-containing group, a nitrogen-containing group, an oxygen-containing group, halogen, nitro, amino, cyano, a boron-containing group, a phosphorus-containing group, a carboxylic acid, an ester, H, NH<NUM>, CN, OH, =O, =S, Cl, I, F,
<CHM>
<CHM>
<CHM>
wherein x is <NUM>, <NUM> or <NUM>, and
R<NUM>-R<NUM> may be present or absent, and if present are selected from alkyl or cycloalkyl containing <NUM>-<NUM> carbon atoms, an aryl group containing <NUM>-<NUM> phenyl rings, alkyl amine, aryl amine, diazo, or alkyl amide containing an alkyl or cycloalkyl containing <NUM>-<NUM> carbon atoms or an aryl group containing <NUM>-<NUM> phenyl rings, and -C≡C-.